feat(dashboard): include custom (BYOK) provider models in combo/alias picker

[uberbyte1805]

Problem

Custom (BYOK) providers — added via Providers → Add OpenAI/Anthropic Compatible — were missing from the model picker in the Combos & Alias page. Their models could not be selected when building combos or aliases, even though the providers were configured and working.

Additionally, model names with nested prefixes (e.g. gnrt/cb/claude-opus-4.6) were truncated to just the first segment (cb) in the picker UI.

Changes

dashboard/src/components/model-picker.tsx

1. useModelCatalog now also fetches /custom-providers and merges their models into the flat catalog. This uses the same pattern as 9router's ModelSelectModal, which fetches custom models in parallel with built-in providers.
2. Model display fix: changed entry.qualified.split("/")[1] → entry.qualified.split("/").slice(1).join("/") so that models with nested path segments (e.g. provider/subprefix/model) display their full sub-path instead of just the first segment after the provider prefix.

dashboard/src/features/providers/page.tsx

• Added a copy-to-clipboard button next to the base URL on each custom provider card, matching the pattern already used on the Endpoints page.

Testing

• ✅ Custom provider models (atmo: 65 models, gnrt: 53 models) now appear in combo/alias picker
• ✅ Model names display correctly (e.g. cb/claude-opus-4.7-1m instead of cb)
• ✅ Combo with BYOK models routes correctly (tested test-byok combo → gnrt/cb/claude-opus-4.7-1m → 200 OK)
• ✅ Fallback strategy works (atmo exhausted → fallback to gnrt → 200 OK)
• ✅ Copy base URL button works on Providers page

Reference

Model picker approach inspired by 9router's ModelSelectModal, which fetches /api/models/custom in parallel and merges with built-in provider models.

[risunCode]

Already fixed in v1.0.5-alpha, thank you