fix: Resolve all lint warnings and type errors across frontend and backend.

Frontend:
- Memoize pagination object in TransactionsTable to prevent unnecessary re-renders and fix exhaustive-deps warning
- Add optional success and message fields to backup API response types for proper error handling

Backend:
- Add TypedDict for transaction type configuration to improve type safety in generate_sample_db
- Fix unpacking of amount_range with explicit float type hints
- Add explicit type hints for descriptions dictionary and specific_descriptions variable
- Fix sync endpoint return types: get_sync_status returns SyncStatus and sync_now returns SyncResult
- Fix transactions endpoint data type declaration to properly support Union types in PaginatedResponse

All checks now pass:
- Frontend: npm lint and npm build ✓
- Backend: mypy type checking ✓
- Backend: ruff lint on modified files ✓

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/src/components/TransactionsTable.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from "react";
+import { useState, useEffect, useMemo } from "react";
 import { useQuery } from "@tanstack/react-query";
 import {
   useReactTable,
@@ -126,16 +126,20 @@ export default function TransactionsTable() {
   });
 
   const transactions = transactionsResponse?.data || [];
-  const pagination = transactionsResponse
-    ? {
-        page: transactionsResponse.page,
-        total_pages: transactionsResponse.total_pages,
-        per_page: transactionsResponse.per_page,
-        total: transactionsResponse.total,
-        has_next: transactionsResponse.has_next,
-        has_prev: transactionsResponse.has_prev,
-      }
-    : undefined;
+  const pagination = useMemo(
+    () =>
+      transactionsResponse
+        ? {
+            page: transactionsResponse.page,
+            total_pages: transactionsResponse.total_pages,
+            per_page: transactionsResponse.per_page,
+            total: transactionsResponse.total,
+            has_next: transactionsResponse.has_next,
+            has_prev: transactionsResponse.has_prev,
+          }
+        : undefined,
+    [transactionsResponse],
+  );
 
   // Check if search is currently debouncing
   const isSearchLoading = filterState.searchTerm !== debouncedSearchTerm;

frontend/src/lib/api.ts

@@ -288,11 +288,14 @@ export const apiClient = {
     return response.data;
   },
 
-  testBackupConnection: async (test: BackupTest): Promise<{ connected?: boolean }> => {
-    const response = await api.post<{ connected?: boolean }>(
-      "/backup/test",
-      test,
-    );
+  testBackupConnection: async (
+    test: BackupTest,
+  ): Promise<{ connected?: boolean; success?: boolean; message?: string }> => {
+    const response = await api.post<{
+      connected?: boolean;
+      success?: boolean;
+      message?: string;
+    }>("/backup/test", test);
     return response.data;
   },
 
@@ -301,11 +304,20 @@ export const apiClient = {
     return response.data;
   },
 
-  performBackupOperation: async (operation: BackupOperation): Promise<{ operation: string; completed: boolean }> => {
-    const response = await api.post<{ operation: string; completed: boolean }>(
-      "/backup/operation",
-      operation,
-    );
+  performBackupOperation: async (
+    operation: BackupOperation,
+  ): Promise<{
+    operation: string;
+    completed: boolean;
+    success?: boolean;
+    message?: string;
+  }> => {
+    const response = await api.post<{
+      operation: string;
+      completed: boolean;
+      success?: boolean;
+      message?: string;
+    }>("/backup/operation", operation);
     return response.data;
   },
 };

leggen/api/models/common.py

@@ -1,4 +1,4 @@
-from typing import Any, Dict, Generic, List, TypeVar
+from typing import Generic, List, TypeVar
 
 from pydantic import BaseModel
 

leggen/api/routes/accounts.py

@@ -246,11 +246,6 @@ async def get_account_transactions(
             offset=offset,
         )
 
-        # Get total count for pagination info
-        total_transactions = await database_service.get_transaction_count_from_db(
-            account_id=account_id,
-        )
-
         data: Union[List[TransactionSummary], List[Transaction]]
 
         if summary_only:
@@ -299,9 +294,7 @@ async def get_account_transactions(
 
 
 @router.put("/accounts/{account_id}")
-async def update_account_details(
-    account_id: str, update_data: AccountUpdate
-) -> dict:
+async def update_account_details(account_id: str, update_data: AccountUpdate) -> dict:
     """Update account details (currently only display_name)"""
     try:
         # Get current account details

leggen/api/routes/backup.py

@@ -129,9 +129,7 @@ async def test_backup_connection(test_request: BackupTest) -> dict:
         success = await backup_service.test_connection(s3_config)
 
         if not success:
-            raise HTTPException(
-                status_code=400, detail="S3 connection test failed"
-            )
+            raise HTTPException(status_code=400, detail="S3 connection test failed")
 
         return {"connected": True}
 
@@ -193,9 +191,7 @@ async def backup_operation(operation_request: BackupOperation) -> dict:
             success = await backup_service.backup_database(database_path)
 
             if not success:
-                raise HTTPException(
-                    status_code=500, detail="Database backup failed"
-                )
+                raise HTTPException(status_code=500, detail="Database backup failed")
 
             return {"operation": "backup", "completed": True}
 
@@ -213,9 +209,7 @@ async def backup_operation(operation_request: BackupOperation) -> dict:
             )
 
             if not success:
-                raise HTTPException(
-                    status_code=500, detail="Database restore failed"
-                )
+                raise HTTPException(status_code=500, detail="Database restore failed")
 
             return {"operation": "restore", "completed": True}
         else:

leggen/api/routes/sync.py

@@ -3,7 +3,7 @@ from typing import Optional
 from fastapi import APIRouter, BackgroundTasks, HTTPException
 from loguru import logger
 
-from leggen.api.models.sync import SchedulerConfig, SyncRequest
+from leggen.api.models.sync import SchedulerConfig, SyncRequest, SyncResult, SyncStatus
 from leggen.background.scheduler import scheduler
 from leggen.services.sync_service import SyncService
 from leggen.utils.config import config
@@ -13,7 +13,7 @@ sync_service = SyncService()
 
 
 @router.get("/sync/status")
-async def get_sync_status() -> dict:
+async def get_sync_status() -> SyncStatus:
     """Get current sync status"""
     try:
         status = await sync_service.get_sync_status()
@@ -78,7 +78,7 @@ async def trigger_sync(
 
 
 @router.post("/sync/now")
-async def sync_now(sync_request: Optional[SyncRequest] = None) -> dict:
+async def sync_now(sync_request: Optional[SyncRequest] = None) -> SyncResult:
     """Run sync synchronously and return results (slower, for testing)"""
     try:
         if sync_request and sync_request.account_ids:

leggen/api/routes/transactions.py

@@ -64,11 +64,9 @@ async def get_all_transactions(
             search=search,
         )
 
-        data: Union[List[TransactionSummary], List[Transaction]]
-
         if summary_only:
             # Return simplified transaction summaries
-            data = [
+            data: list[TransactionSummary | Transaction] = [
                 TransactionSummary(
                     transaction_id=txn["transactionId"],  # NEW: stable bank-provided ID
                     internal_transaction_id=txn.get("internalTransactionId"),

leggen/commands/generate_sample_db.py

@@ -5,11 +5,19 @@ import random
 import sqlite3
 from datetime import datetime, timedelta
 from pathlib import Path
-from typing import Any
+from typing import Any, TypedDict
 
 import click
 
 
+class TransactionType(TypedDict):
+    """Type definition for transaction type configuration."""
+
+    description: str
+    amount_range: tuple[float, float]
+    frequency: float
+
+
 class SampleDataGenerator:
     """Generates realistic sample data for testing Leggen."""
 
@@ -42,7 +50,7 @@ class SampleDataGenerator:
             },
         ]
 
-        self.transaction_types = [
+        self.transaction_types: list[TransactionType] = [
             {
                 "description": "Grocery Store",
                 "amount_range": (-150, -20),
@@ -227,6 +235,8 @@ class SampleDataGenerator:
                 )[0]
 
                 # Generate transaction amount
+                min_amount: float
+                max_amount: float
                 min_amount, max_amount = transaction_type["amount_range"]
                 amount = round(random.uniform(min_amount, max_amount), 2)
 
@@ -245,7 +255,7 @@ class SampleDataGenerator:
                 internal_transaction_id = f"int-txn-{random.randint(100000, 999999)}"
 
                 # Create realistic descriptions
-                descriptions = {
+                descriptions: dict[str, list[str]] = {
                     "Grocery Store": [
                         "TESCO",
                         "SAINSBURY'S",
@@ -273,7 +283,7 @@ class SampleDataGenerator:
                     "Transfer to Savings": ["SAVINGS TRANSFER", "INVESTMENT TRANSFER"],
                 }
 
-                specific_descriptions = descriptions.get(
+                specific_descriptions: list[str] = descriptions.get(
                     transaction_type["description"], [transaction_type["description"]]
                 )
                 description = random.choice(specific_descriptions)

tests/conftest.py

@@ -8,8 +8,10 @@ from pathlib import Path
 from unittest.mock import patch
 
 import pytest
+import tomli_w
 from fastapi.testclient import TestClient
 
+from leggen.commands.server import create_app
 from leggen.utils.config import Config
 
 # Create test config before any imports that might load it
@@ -27,15 +29,12 @@ _config_data = {
     "scheduler": {"sync": {"enabled": True, "hour": 3, "minute": 0}},
 }
 
-import tomli_w
 with open(_test_config_path, "wb") as f:
     tomli_w.dump(_config_data, f)
 
 # Set environment variables to point to test config BEFORE importing the app
 os.environ["LEGGEN_CONFIG_FILE"] = str(_test_config_path)
 
-from leggen.commands.server import create_app
-
 
 def pytest_configure(config):
     """Pytest hook called before test collection."""
@@ -114,7 +113,9 @@ def mock_auth_token(temp_config_dir):
 def fastapi_app(mock_db_path):
     """Create FastAPI test application."""
     # Patch the database path for the app
-    with patch("leggen.utils.paths.path_manager.get_database_path", return_value=mock_db_path):
+    with patch(
+        "leggen.utils.paths.path_manager.get_database_path", return_value=mock_db_path
+    ):
         app = create_app()
         yield app
 

tests/unit/test_api_backup.py

@@ -211,10 +211,7 @@ class TestBackupAPI:
         assert response.status_code == 200
         data = response.json()
         assert len(data) == 2
-        assert (
-            data[0]["key"]
-            == "leggen_backups/database_backup_20250101_120000.db"
-        )
+        assert data[0]["key"] == "leggen_backups/database_backup_20250101_120000.db"
 
     def test_list_backups_no_config(self, api_client, mock_config):
         """Test backup listing with no configuration."""

tests/unit/test_api_transactions.py

@@ -157,7 +157,6 @@ class TestTransactionsAPI:
             )
 
         assert response.status_code == 200
-        data = response.json()
 
         # Verify the database service was called with correct filters
         mock_get_transactions.assert_called_once_with(