feat: surface saved endpoint models and revamp the admin UI

feat: numbered OpenAI-compatible endpoints admin page

Add Azure OpenAI provider (#1284)

Add ChatGPT OAuth as an OpenAI Codex provider (#1279)

Add Google Vertex AI with renewable ADC (#1193)

Remove the native Anthropic provider transport (#1067)

Make provider capabilities semantic and typed (#1047)

Establish single-owner runtime with stream-safe provider hot swaps (#1036)