feat(docker-watcher): phase 5 - registry client & poller

Gitea registry client with tag listing and pattern matching, cron-based
polling scheduler with first-poll safety, poll state persistence.
DeployTriggerer interface for decoupled deploy triggering.

internal/store/registries.go

@@ -41,6 +41,22 @@ func (s *Store) GetRegistryByID(id string) (Registry, error) {
 	return r, nil
 }
 
+// GetRegistryByName returns a single registry by its unique name.
+func (s *Store) GetRegistryByName(name string) (Registry, error) {
+	var r Registry
+	err := s.db.QueryRow(
+		`SELECT id, name, url, type, token, created_at, updated_at
+		 FROM registries WHERE name = ?`, name,
+	).Scan(&r.ID, &r.Name, &r.URL, &r.Type, &r.Token, &r.CreatedAt, &r.UpdatedAt)
+	if errors.Is(err, sql.ErrNoRows) {
+		return Registry{}, fmt.Errorf("registry %q: %w", name, ErrNotFound)
+	}
+	if err != nil {
+		return Registry{}, fmt.Errorf("query registry by name: %w", err)
+	}
+	return r, nil
+}
+
 // GetAllRegistries returns every registry ordered by name.
 func (s *Store) GetAllRegistries() ([]Registry, error) {
 	rows, err := s.db.Query(