Refactor search into source-specific collectors

TODO.md

@@ -88,6 +88,23 @@
   - Artgrid hover-video preview cannot be derived reliably from the provided snapshot alone
   - if Artgrid preview video is still required, the next useful artifact is a browser HAR or DevTools network capture from an opened clip page
 
+## Current Session Update (2026-03-13, Collector Refactor)
+- Refactored the search pipeline into source-specific collectors:
+  - `envatoCollector`
+  - `artgridCollector`
+  - `googleVideoCollector`
+- `SearchService` now acts mainly as:
+  - collector orchestration
+  - query-pass control
+  - dedupe
+  - cross-source enrichment scheduling
+- Goal of the refactor:
+  - reduce cross-source coupling
+  - make future source-specific fixes safer
+  - make it easier to replace or disable one source without destabilizing the others
+- Current implementation note:
+  - collectors are still in Go code under backend services, but the responsibilities are now separated by source instead of one monolithic search loop
+
 ## Local Self-Test Workflow
 - Primary command:
   - `bash scripts/selftest.sh`