Refactor settings system and improve context initialization

Backend:
- Add type validation and coercion for settings API
- Implement SettingStorage and SettingType in registry
- Improve CRUD operations for settings

Frontend:
- Refactor Theme, Language, Sidebar, ViewMode contexts
- Simplify admin components (GeneralTab, SettingsTab, UsersTab)
- Add new settings endpoints to API client
- Improve App initialization flow

Infrastructure:
- Update Dockerfile and docker-compose.yml
- Add .dockerignore
- Update Makefile and README

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

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

backend/app/api/v1/auth.py

@@ -33,12 +33,17 @@ def register(
     
     # If not the first user, check if registration is enabled
     if not is_first_user:
-        registration_enabled = crud.settings.get_setting_value(
+        registration_enabled_raw = crud.settings.get_setting_value(
             db, 
             key="registration_enabled", 
             default=True  # Default to enabled if setting doesn't exist
         )
         
+        if isinstance(registration_enabled_raw, str):
+            registration_enabled = registration_enabled_raw.strip().lower() in ("true", "1")
+        else:
+            registration_enabled = bool(registration_enabled_raw)
+
         if not registration_enabled:
             raise HTTPException(
                 status_code=status.HTTP_403_FORBIDDEN,
@@ -146,10 +151,15 @@ def get_registration_status(
     This is a public endpoint that doesn't require authentication.
     Returns the registration_enabled setting value.
     """
-    registration_enabled = crud.settings.get_setting_value(
+    registration_enabled_raw = crud.settings.get_setting_value(
         db,
         key="registration_enabled",
         default=True
     )
 
+    if isinstance(registration_enabled_raw, str):
+        registration_enabled = registration_enabled_raw.strip().lower() in ("true", "1")
+    else:
+        registration_enabled = bool(registration_enabled_raw)
+
     return {"registration_enabled": registration_enabled}