feat: Remove URL rewriting in favor of proper nextcloud config

Remove URL rewriting logic from MCP server that was converting
      public URLs to internal Docker URLs. This was a workaround for
      Nextcloud's overwritehost setting forcing URLs to localhost:8080.

      Changes:
      - Remove OIDC endpoint rewriting in app.py (setup_oauth_config)
      - Remove OIDC_JWKS_URI override support (no longer needed)
      - Remove URL rewriting in browser_oauth_routes.py
      - Remove URL rewriting in token_broker.py
      - Update Helm chart values and README
      - Add hybrid auth setup unit tests
      - Update Astrolabe admin UI for Vue 3

      The proper fix is in the previous commit which removes the
      overwritehost setting from Nextcloud, allowing it to respect
      the Host header from incoming requests.

third_party/astrolabe/lib/Controller/ApiController.php

@@ -265,6 +265,14 @@ class ApiController extends Controller {
 	public function serverStatus(): JSONResponse {
 		$status = $this->client->getStatus();
 
+		// Validate that status is an array before accessing
+		if (!is_array($status)) {
+			return new JSONResponse([
+				'success' => false,
+				'error' => 'Invalid response from MCP server'
+			], Http::STATUS_INTERNAL_SERVER_ERROR);
+		}
+
 		if (isset($status['error'])) {
 			return new JSONResponse([
 				'success' => false,
@@ -289,6 +297,14 @@ class ApiController extends Controller {
 	public function adminVectorStatus(): JSONResponse {
 		$status = $this->client->getVectorSyncStatus();
 
+		// Validate that status is an array before accessing
+		if (!is_array($status)) {
+			return new JSONResponse([
+				'success' => false,
+				'error' => 'Invalid response from MCP server'
+			], Http::STATUS_INTERNAL_SERVER_ERROR);
+		}
+
 		if (isset($status['error'])) {
 			return new JSONResponse([
 				'success' => false,