⚙️ perf: reduce first-load MongoDB round trips (#14101)

* perf(api): reduce first-load database round trips

* docs: move agent guidance to claude docs

* refactor(api): move message validation into api package

* fix(api): narrow active generation job lookup

* fix(api): preserve omitted source identity

api/server/services/Config/loadDefaultModels.js

@@ -4,6 +4,7 @@ const {
   mergeHeaders,
   getAnthropicModels,
   getBedrockModels,
+  getAppConfigOptionsFromUser,
   getOpenAIModels,
   getGoogleModels,
 } = require('@librechat/api');
@@ -17,13 +18,7 @@ const { getAppConfig } = require('./app');
  */
 async function loadDefaultModels(req) {
   try {
-    const appConfig =
-      req.config ??
-      (await getAppConfig({
-        role: req.user?.role,
-        userId: req.user?.id,
-        tenantId: req.user?.tenantId,
-      }));
+    const appConfig = req.config ?? (await getAppConfig(getAppConfigOptionsFromUser(req.user)));
     const vertexConfig = appConfig?.endpoints?.[EModelEndpoint.anthropic]?.vertexConfig;
 
     /** Forward configured custom headers (endpoint over global `all`) so model