Add per-store test_query for automated store testing

Each store can now have its own test_query (e.g., "logitech" for
electronics stores). The "Test All" button uses each store's
configured query instead of prompting — just click and watch.

- Add test_query column (migration 003)
- Add field to YAML sync, store forms, and route schema
- Set test_query in HG Spot and Links.hr configs
- Test All runs immediately using per-store queries
- Hover test result to see which query was used

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stores/hgspot.yaml

@@ -4,6 +4,7 @@ search_url: https://www.hgspot.hr/pretraga?q={query}&page=0
 category: Electronics
 currency: EUR
 render_js: true
+test_query: logitech
 rate_limit: 1
 
 selectors:

stores/links-hr.yaml

@@ -3,6 +3,7 @@ base_url: https://www.links.hr
 search_url: https://www.links.hr/hr/search?q={query}
 category: Electronics
 currency: EUR
+test_query: logitech
 
 selectors:
   container: ".card.mobile-card"