Add card MCP tools integration and fix ServiceClient methods

### MCP Server Enhancement:
- Add 3 new card-related MCP tools: get_user_cards, draw_card, get_draw_status
- Fix ServiceClient missing methods for ai.card API integration
- Total MCP tools now: 20 (including card functionality)

### ServiceClient Fixes:
- Add get_user_cards() method for card collection retrieval
- Add draw_card() method for gacha functionality
- Fix JSON Value handling in card count display

### Integration Success:
- ai.gpt MCP server successfully starts with all 20 tools
- HTTP endpoints properly handle card-related requests
- Ready for ai.card server connection on port 8000

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

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

Cargo.toml

@@ -31,3 +31,7 @@ axum = "0.7"
 tower = "0.4"
 tower-http = { version = "0.5", features = ["cors"] }
 hyper = "1.0"
+
+# OpenAI API client
+async-openai = "0.23"
+openai_api_rust = "0.1"