refactor: Remove file locking mechanism from usage data saving

feat: Enhance daily reset logic to ensure timezone-aware date handling

fix: Handle missing cooldown values in UsageManager to prevent key lockout type errors

feat: Update key release logic in RotatingClient and UsageManager to support model-specific tracking

feat: Enhance error classification and handling in UsageManager and error_handler for improved retry logic and cooldown management

feat: Enhance asynchronous handling in RotatingClient and UsageManager for improved error management and usage tracking

feat: Improve key acquisition logic in RotatingClient and UsageManager for better async handling and error management

feat: Enhance error handling in UsageManager to extract retry delay from multiple error message formats

feat: Refactor logging to use a dedicated logger across providers and enhance model retrieval with httpx

feat: Implement per-model API key cooldowns

feat(multi-provider): Implement dynamic API key loading and new endpoints

feat: Implement robust API key rotation, retry, and logging

Inital commit