Integrate Bootstrap 5 and Bootstrap Icons into UI

- Add Bootstrap 5.3.3 + Icons via CDN to base.html
- Replace 315-line hand-written CSS with 35-line brand overrides
- Update all 13 templates with Bootstrap utility classes:
  - Responsive navbar with mobile hamburger menu
  - Consistent card-based layout for forms and profile
  - Proper button alignment with d-flex and d-grid utilities
  - List groups for data display (profile info)
  - Professional alerts and icons
- No backend changes, no build toolchain needed
- Responsive design works on mobile/tablet/desktop

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

web/config.py

@@ -7,7 +7,7 @@ class Settings(BaseSettings):
     BASE_URL: str = "http://localhost:8000"
     PASSWORD_RESET_EXPIRE_MINUTES: int = 60
 
-    model_config = {"env_file": ".env"}
+    model_config = {"env_file": ".env", "case_sensitive": False}
 
 
 settings = Settings()