feat: saved searches (bookmarks)

- Add saved_searches_collection to database.py with index on created_by+created_at
- New routes/saved_searches.py: GET /api/saved-searches, POST, DELETE
- Saved searches are scoped per user (created_by = token sub)
- Mount router in main.py
- Frontend: Save filters button, saved search pills with load/delete
- loadSavedSearches called on initApp
- applySavedSearch restores filters and validates services against current options
- Add CSS for saved-searches row
- Add tests for CRUD, delete 404, and name validation

backend/frontend/style.css

@@ -370,6 +370,14 @@ input {
   align-items: center;
 }
 
+.saved-searches {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  align-items: center;
+  font-size: 13px;
+}
+
 .modal__explanation {
   background: rgba(255, 255, 255, 0.03);
   border: 1px solid var(--border);