Fix 11 bugs in polymarket market maker bot

[jme21]

Critical fixes:

• Fix invalid orderbook validation (best_ask <= 1 -> best_ask >= 1)
• Fix async/sync mismatch in WebSocket handler using inspect.iscoroutinefunction
• Add inventory update mechanism via trade handler

Medium fixes:

• Fix division by zero in get_quote_size_no when price >= 1.0
• Fix WebSocket reconnection to resubscribe to all channels
• Fix wrong cancelled count in batch_cancel_orders
• Fix pending cancellations memory leak by cleaning up after single cancels

Minor fixes:

• Fix load_dotenv() order (move before get_settings)
• Add metrics recording for orders, fills, cancellations, spread
• Fix WebSocket type hint (WebSocketClientProtocol instead of Server)
• Remove unused imports (Any, BaseModel) from config.py