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/core/settings_registry.py

@@ -328,15 +328,16 @@ register_setting(SettingDefinition(
 
 
 # =============================================================================
-# USER-SPECIFIC SETTINGS (Per-user, Database)
-# These settings can be different for each user
+# USER-SPECIFIC SETTINGS (Frontend localStorage)
+# These settings are managed by the frontend per-browser/user-session.
+# If you need cross-device persistence, implement a per-user DB table + API.
 # =============================================================================
 
 register_setting(SettingDefinition(
     key="user_theme_mode",
     type=SettingType.STRING,
     scope=SettingScope.USER_SPECIFIC,
-    storage=SettingStorage.DATABASE,
+    storage=SettingStorage.LOCAL_STORAGE,
     default="system",
     description="User's preferred theme mode (light/dark/system)",
     category="user_preferences",
@@ -348,7 +349,7 @@ register_setting(SettingDefinition(
     key="user_language",
     type=SettingType.STRING,
     scope=SettingScope.USER_SPECIFIC,
-    storage=SettingStorage.DATABASE,
+    storage=SettingStorage.LOCAL_STORAGE,
     default="en",
     description="User's preferred language",
     category="user_preferences",
@@ -360,7 +361,7 @@ register_setting(SettingDefinition(
     key="user_sidebar_collapsed",
     type=SettingType.BOOLEAN,
     scope=SettingScope.USER_SPECIFIC,
-    storage=SettingStorage.DATABASE,
+    storage=SettingStorage.LOCAL_STORAGE,
     default=False,
     description="User's sidebar collapsed state preference",
     category="user_preferences",
@@ -371,7 +372,7 @@ register_setting(SettingDefinition(
     key="user_view_mode",
     type=SettingType.STRING,
     scope=SettingScope.USER_SPECIFIC,
-    storage=SettingStorage.DATABASE,
+    storage=SettingStorage.LOCAL_STORAGE,
     default="admin",
     description="User's current view mode (admin/user)",
     category="user_preferences",