Fix frontend errors and pydantic config for local development

Frontend fixes:
- Copy missing JS files from blackroad-os/ to backend/static/js/
  - os.js (core OS functionality)
  - components.js (UI components)
  - registry.js (app registry)
  - app.js, config.js, theme.js, mock_data.js (supporting files)
- Fixes 3 ERROR findings from Cece audit
- System health: 0 ERRORS → 94 SUCCESSES (from 91)

Backend config fix:
- Add `extra = "ignore"` to Settings.Config in backend/app/config.py
- Allows .env.example to have more vars than Settings class defines
- Fixes Pydantic v2 validation errors on startup
- Enables local development without removing env template vars

Cece audit results after fixes:
🔴 CRITICAL: 0
🟠 ERROR:    0 (was 3)
🟡 WARNING:  6
🟢 SUCCESS:  94 (was 91)

backend/app/config.py

@@ -63,6 +63,7 @@ class Settings(BaseSettings):
     class Config:
         env_file = ".env"
         case_sensitive = True
+        extra = "ignore"  # Allow extra env vars in .env file
 
 
 settings = Settings()