chore(F.4e): remove env-based site loading, unify OAuth Clients, update docs

- Remove env-based site discovery from SiteManager and ProjectManager
- Unify admin and user OAuth Clients into single role-based page
- Update all documentation to reflect DB-based site management
- Clean up env.example, README, ARCHITECTURE docs
- Improve Projects page empty state with link to My Sites
- Remove obsolete env discovery tests

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugins/supabase/handlers/auth.py

@@ -483,6 +483,8 @@ async def delete_user_factor(client: SupabaseClient, user_id: str, factor_id: st
         return json.dumps({"success": False, "error": str(e)}, indent=2, ensure_ascii=False)
 
 
+
+
 async def search_users(
     client: SupabaseClient, query: str, page: int = 1, per_page: int = 50
 ) -> str: