Reduce search timeout pressure on reverted baseline

TODO.md

@@ -624,6 +624,34 @@
 - If behavior in the browser does not match the latest backend/frontend code, the first assumption should be stale frontend assets until proven otherwise
 
 ## Recent Change Log
+- Date: `2026-03-18`
+- What changed:
+  - Resumed and completed the interrupted search-timeout mitigation work that had been left locally after the rollback to `f131cee`.
+  - Split the search-service deadline into:
+    - collection deadline
+    - enrichment deadline with a reserved window
+  - Reduced collector fan-out on the reverted baseline:
+    - fewer base queries
+    - no per-request query shuffling
+    - earlier stop when a collector repeatedly returns `0` results before producing any accepted item
+  - Raised `Google Video` max results to `12` so visible count does not collapse as hard when Envato / Artgrid are cold.
+  - Added unit coverage for the search/enrichment deadline split helper.
+- Why it changed:
+  - The user-provided log `ai-media-hub-2026-03-18T04-44-11-440Z.log` showed:
+    - repeated collector passes with many `rawCount: 0`
+    - `search_service:deadline_reached`
+    - `partialDueToDeadline: true`
+    - final warning `search returned partial results to avoid gateway timeout`
+    - only `Google Video` surviving into the final result set with `resultCount: 8`
+  - The real bottleneck in that log was collector-side time waste before enrichment/Gemini, not another Gemini output-format issue.
+- How it was verified:
+  - PowerShell with repo-local tooling:
+    - `go test ./...`
+    - `node --check frontend/app.js`
+- What is still risky or incomplete:
+  - This should reduce timeout pressure and improve visible count in the common “Envato/Artgrid zero streak” case, but upstream SearXNG quality can still dominate the final pool.
+  - A full app-boot smoke flow was not reintroduced into this reverted baseline in this turn.
+
 - Date: `2026-03-17`
 - What changed:
   - Reverted commit `5ca7aef` (`Strengthen search breadth and modal fitting`) to restore the previous stable search/modal baseline.