refactor: remove unused OPENAI_API_KEY and GOOGLE_API_KEY

Removed all references to OPENAI_API_KEY and GOOGLE_API_KEY since only
Claude (Anthropic) provider is implemented. These were placeholder references
for future providers that don't exist yet.

Changes:
- Removed OPENAI_API_KEY and GOOGLE_API_KEY from docker-compose.yml
- Removed from .env and .env.example files
- Updated setup/routes/store-api-key.ts to only support anthropic
- Updated setup/routes/delete-api-key.ts to only support anthropic
- Updated setup/routes/api-keys.ts to only return anthropic key status
- Updated models/routes/providers.ts to only list anthropic provider
- Updated auto-mode-service.ts error message to only reference ANTHROPIC_API_KEY

Backend test results: 653/653 passing ✅

🤖 Generated with Claude Code

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

apps/server/src/routes/models/routes/providers.ts

@@ -17,10 +17,6 @@ export function createProvidersHandler() {
           available: statuses.claude?.installed || false,
           hasApiKey: !!process.env.ANTHROPIC_API_KEY,
         },
-        google: {
-          available: !!process.env.GOOGLE_API_KEY,
-          hasApiKey: !!process.env.GOOGLE_API_KEY,
-        },
       };
 
       res.json({ success: true, providers });