ui: Refactor models store, MCP service, and gate logs behind VITE_DEBUG (#23236)

* refactor: Scope console logs to `DEV` + `VITE_DEBUG` env vars

* refactor: skip MCP proxy probe when no server requires it

* refactor: suppress expected disconnect errors during MCP client shutdown

* refactor: Deduplicate requests

* refactor: deduplicate model fetching across ROUTER and MODEL modes

* refactor: Clean up models logic

* chore: Add `.env.example` file

* refactor: replace client-side CORS proxy probe with server status flag

* refactor: Post-review fixes

* test: add vitest client setup with API fetch mocks

tools/server/server-models.cpp

@@ -1165,6 +1165,7 @@ void server_models_routes::init_routes() {
                 // Deprecated: use ui_settings instead (kept for backward compat)
                 {"webui_settings",  webui_settings},
                 {"build_info",     std::string(llama_build_info())},
+                {"cors_proxy_enabled", params.ui_mcp_proxy || params.webui_mcp_proxy},
             });
             return res;
         }