Ship production optimization M1-M12.5A: queues, metrics, HTTP observability, and vector search reliability.

Keep similar-ai from tripping the global circuit on a lone URL 502, clamp Qdrant search to 100, and add Server-Timing plus slow-request logging. Studio shared props, Academy S3 exists caching, heat chunking, and Redis/scheduler hygiene stay in this rollout.

config/http_observability.php

@@ -0,0 +1,14 @@
+<?php
+
+declare(strict_types=1);
+
+return [
+    'slow_request' => [
+        'enabled' => (bool) env('HTTP_SLOW_REQUEST_LOG_ENABLED', false),
+        'threshold_ms' => (int) env('HTTP_SLOW_REQUEST_MS', 750),
+        /*
+         * Testing only. When set, replaces measured duration so tests do not sleep.
+         */
+        'test_duration_ms' => env('HTTP_SLOW_REQUEST_TEST_DURATION_MS'),
+    ],
+];