Add profile-driven feature runtime utilities

- Add feature_registry.py with FeatureGroup definitions for core, podcast, youtube, content_planning
- Add feature_profiles.py to parse ALWRITY_FEATURE_TO_ENABLE env var
- Add feature_runtime.py with is_enabled(), get_enabled_routers() helpers
- Fix syntax error in __init__.py (duplicate OnboardingManager)

Enables feature toggles via ALWRITY_FEATURE_TO_ENABLE environment variable.

backend/alwrity_utils/__init__.py

@@ -12,6 +12,14 @@ from .rate_limiter import RateLimiter
 from .frontend_serving import FrontendServing
 from .router_manager import RouterManager
 from .onboarding_manager import OnboardingManager
+from .feature_runtime import (
+    get_active_profiles,
+    get_enabled_groups,
+    get_enabled_optional_services,
+    get_enabled_routers,
+    get_enabled_startup_hooks,
+    is_enabled,
+)
 
 __all__ = [
     'DependencyManager',
@@ -22,5 +30,11 @@ __all__ = [
     'RateLimiter',
     'FrontendServing',
     'RouterManager',
-    'OnboardingManager'
+    'OnboardingManager',
+    'get_active_profiles',
+    'get_enabled_groups',
+    'get_enabled_optional_services',
+    'get_enabled_routers',
+    'get_enabled_startup_hooks',
+    'is_enabled'
 ]