Implement data completeness dashboard backend

Adds and fixes a comprehensive data completeness analysis flow:
- Preps migration to create analyze_data_completeness function with weighted scoring
- Addresses security warning by constraining search_path to public schema
- Lays groundwork for real-time updates and integration with admin UI (backfills, filters)

src/integrations/supabase/types.ts

@@ -6628,6 +6628,17 @@ export type Database = {
       }
     }
     Functions: {
+      analyze_data_completeness: {
+        Args: {
+          p_entity_type?: string
+          p_limit?: number
+          p_max_score?: number
+          p_min_score?: number
+          p_missing_category?: string
+          p_offset?: number
+        }
+        Returns: Json
+      }
       anonymize_user_submissions: {
         Args: { target_user_id: string }
         Returns: undefined