[Error Handling] Provide specific feedback for "Insufficient Quota" or Payment errors

[MXD66]

Is your feature request related to a problem? Please describe.
Yes. Currently, when the underlying model provider (e.g., OpenAI, DeepSeek) refuses a request due to insufficient funds, quota limits, or account arrears, the chat interface fails silently or returns a generic error. This makes it impossible for the user to distinguish between a temporary network connection issue, a bug, or an actual payment issue with their API provider.

Describe the solution you'd like
I would like the system to parse error responses from the model provider more granularly.

1. Error Detection: Specifically catch payment-related error codes (such as HTTP 402 Payment Required or provider-specific codes like insufficient_quota).
2. User Feedback: Instead of a generic failure, display a specific, actionable error message in the chat interface: "Current model quota is insufficient or the account is in arrears. Please check your provider balance."

Describe alternatives you've considered
None.

Additional context
This is particularly important for API-based usage (like OpenAI or DeepSeek) where users manage their own billing, as running out of credits is a common occurrence.