feat(frontend): Update brand identity with new logo and color scheme.

- Add new Logo component with gradient design (blue #0b74de to cyan #06b6d4)
- Replace CreditCard icon with custom Logo in sidebar
- Update primary and secondary theme colors to match brand gradient
- Regenerate all PWA icons with new logo design
- Update theme colors in PWA manifest and meta tags
- Fix ESLint config to ignore generated PWA files

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

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

frontend/vite.config.ts

@@ -15,7 +15,7 @@ export default defineConfig({
         name: "Leggen",
         short_name: "Leggen",
         description: "Personal finance management application",
-        theme_color: "#ffffff",
+        theme_color: "#0b74de",
         background_color: "#ffffff",
         display: "standalone",
         orientation: "portrait",