Add schema cache fallback for service account JSON

- Add fallback RPC method when PostgREST schema cache fails
- Save service account JSON separately via raw SQL
- Show warning message if manual save needed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

verify-column.sql

@@ -0,0 +1,10 @@
+-- Check if column exists in database
+SELECT 
+    column_name,
+    data_type,
+    is_nullable,
+    column_default
+FROM information_schema.columns 
+WHERE table_schema = 'public'
+AND table_name = 'platform_settings'
+ORDER BY ordinal_position;