fix: Fix proxy reload and invalid-credential retries

[highkay]

Summary

• hot-reload proxy directory state so runtime proxy changes take effect without keeping stale affinities alive
• retry on upstream invalid-credential 400 responses by switching to another token instead of failing the request immediately
• add compatibility for socks:// aliases and Responses API input_image normalization

Validation

• python3 -m py_compile app/control/proxy/init.py app/control/proxy/scheduler.py app/dataplane/proxy/init.py app/dataplane/proxy/adapters/session.py app/dataplane/reverse/transport/websocket.py app/products/openai/chat.py app/products/openai/responses.py app/products/anthropic/messages.py