* feat(models): unify provider metadata around backend catalog
- Move shared provider metadata and alias normalization into backend-owned provider catalog
- Expose display, fetch, auth, and default model metadata through /api/models provider_options
- Replace frontend static provider registry with catalog-driven selection, validation, grouping, and fallback rendering
- Treat provider default api_base as placeholder and effective fetch/test base while keep submitted api_base separate from derived defaults
- Add model page retry handling, touched locale updates, and provider metadata assertions in backend tests
* fix(models): canonicalize backend provider aliases and common models
* fix(models): restore deepseek common model recommendations
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