refactor: Unify leggen and leggend packages into single leggen package

- Merge leggend API components into leggen (api/, services/, background/)
- Replace leggend command with 'leggen server' subcommand
- Consolidate configuration systems into leggen.utils.config
- Update environment variables: LEGGEND_API_URL -> LEGGEN_API_URL
- Rename LeggendAPIClient -> LeggenAPIClient
- Update all documentation, Docker configs, and compose files
- Fix all import statements and test references
- Remove duplicate utility files and clean up package structure

All tests passing (101/101), linting clean, server functionality preserved.

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

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

leggen/commands/status.py

@@ -1,7 +1,7 @@
 import click
 
 from leggen.main import cli
-from leggen.api_client import LeggendAPIClient
+from leggen.api_client import LeggenAPIClient
 from leggen.utils.text import datefmt, echo, info, print_table
 
 
@@ -11,12 +11,12 @@ def status(ctx: click.Context):
     """
     List all connected banks and their status
     """
-    api_client = LeggendAPIClient(ctx.obj.get("api_url"))
+    api_client = LeggenAPIClient(ctx.obj.get("api_url"))
 
-    # Check if leggend service is available
+    # Check if leggen server is available
     if not api_client.health_check():
         click.echo(
-            "Error: Cannot connect to leggend service. Please ensure it's running."
+            "Error: Cannot connect to leggen server. Please ensure it's running."
         )
         return