feat(server): converge legacy compatibility (#15426)

#### PR Dependency Tree


* **PR #15426** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added workspace BYOK profiles with provider/model catalogs, capability
validation, connection probing, credential rotation, reordering, and
secure local leases.
* Added Copilot route options, selectable targets, managed tiers,
explicit profile/model overrides, and improved streaming with tool
callbacks and abort support.
* Added Copilot availability controls to prevent access when the feature
is disabled.
* **Changes**
* Simplified Copilot configuration and removed legacy provider-specific
settings.
* Removed obsolete model, token-cost, transcript strategy, and provider
metadata fields from public responses.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/admin/src/config.json

@@ -389,39 +389,6 @@
       "type": "Array",
       "desc": "The profile list for copilot providers."
     },
-    "providers.defaults": {
-      "type": "Object",
-      "desc": "The default provider ids for model output types and global fallback."
-    },
-    "providers.openai": {
-      "type": "Object",
-      "desc": "The config for the openai provider.",
-      "link": "https://github.com/openai/openai-node"
-    },
-    "providers.cloudflareWorkersAi": {
-      "type": "Object",
-      "desc": "The config for the Cloudflare Workers AI provider."
-    },
-    "providers.fal": {
-      "type": "Object",
-      "desc": "The config for the fal provider."
-    },
-    "providers.gemini": {
-      "type": "Object",
-      "desc": "The config for the gemini provider."
-    },
-    "providers.geminiVertex": {
-      "type": "Object",
-      "desc": "The config for the gemini provider in Google Vertex AI."
-    },
-    "providers.anthropic": {
-      "type": "Object",
-      "desc": "The config for the anthropic provider."
-    },
-    "providers.anthropicVertex": {
-      "type": "Object",
-      "desc": "The config for the anthropic provider in Google Vertex AI."
-    },
     "unsplash": {
       "type": "Object",
       "desc": "The config for the unsplash key."