fix: refine upstream model sync and binding UI

[chenyme]

Summary

This PR improves upstream model and route-binding management in the admin console.

It fixes generic request validation errors so upstream creation/edit forms now show field-level messages, such as invalid baseURL, missing apiKeys, or invalid JSON-related fields. It also refines the upstream model sync and route-binding flow: the route-binding table now focuses on configured bindings, deleted bindings no longer leave confusing unbound rows in the main binding list, sync remains the path for rebinding available upstream models, and parent upstream counts refresh after binding changes.

Change type

• Bug fix
• Feature
• Documentation
• Refactor
• Configuration / deployment
• Security hardening
• Other

Affected areas

• Frontend / UI
• Backend / API
• Authentication / authorization
• Conversations / streaming
• Files / RAG / extraction
• Model routing / providers
• MCP / tools
• Billing / payments
• Admin console
• Deployment / Docker / configuration
• Documentation

Verification

• cd frontend && pnpm lint
• cd backend && go test ./...
• git diff --check

Screenshots, API examples, or logs

N/A

Configuration, migration, and compatibility notes

No configuration or database migration changes are required.

The upstream route status query now supports the configured-binding view used by the admin UI. Existing upstream model catalogs and route bindings remain compatible.

Documentation

• Documentation is not needed for this change.
• Documentation was updated.
• Documentation still needs to be updated.

Security and privacy

• No secrets, tokens, credentials, local config, or personal data are included.
• User data access remains scoped by authenticated user context unless an admin-only path explicitly requires broader access.
• Security-sensitive behavior was reviewed, including authentication, authorization, provider routing, file processing, billing, and admin APIs where relevant.

Checklist

• I searched existing issues and pull requests.
• Changes are focused and do not include unrelated refactors.
• Tests or static verification were run where practical.
• User-facing behavior, deployment steps, API contracts, or configuration changes are documented.
• Generated artifacts are included only when this project explicitly requires them.
• Caches, build output, .pyc files, .env files, and local storage data are not committed.