feat(A5): add app_config table + typed config service
- Migration 034: creates app_config table with JSONB columns (render, storage,
worker, notifications, billing); migrates existing system_settings values
- backend/app/core/config_service.py:
- Typed Pydantic models: RenderConfig, WorkerConfig, StorageConfig, etc.
- AppConfig aggregate model
- get_app_config(db) async + get_app_config_sync() for Celery tasks
- update_render_config() / update_worker_config() for partial updates
- system_settings table preserved for backward compat during Phase B migration
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Hartmut
5764118b8e