Add refresh from source for entries and whole lists

- Every provider can look an entry up again by its ID (TMDB, TheTVDB,
  IGDB, Deezer, MusicBrainz, Wikipedia); search and lookup share parsing
- POST /api/items/{id}/refresh re-applies title, subtitle, year,
  description, link, details and artwork. Kept: the "why" note, rank,
  theater production/venue/cast and a theater entry's year, the Deezer
  preview match. Empty source fields don't erase existing values
- New items.image_custom column (migration 4; existing uploads marked)
  records artwork the owner chose; refresh keeps it unless asked
- Refused for custom lists and hand-added entries; entries the source
  dropped are reported, and a refresh whose title shares no words with
  the current one is rejected as a likely bad ID
- Editor: refresh button per row (asks about the owner's own artwork),
  and "Refresh all" with a confirm step, replace-my-art checkbox,
  progress with Stop, and a summary of problems

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/providers/live_test.go

@@ -62,3 +62,33 @@ func pick(res []Result, i int) Result {
 	}
 	return res[i]
 }
+
+func TestLiveLookup(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancel()
+	reg := NewRegistry(func(context.Context) Credentials { return Credentials{} })
+	for _, c := range []struct{ category, provider, id, want string }{
+		{"album", "deezer", "album:14590454", "Death Magnetic"},
+		{"song", "deezer", "track:63480987", "Dreams"},
+		{"album", "musicbrainz", "release-group:5c8a25bf-4764-3cce-8f37-30af79d3b101", "Death Magnetic"},
+		{"theater", "wikipedia", "1678965", "Wicked"},
+	} {
+		res, err := reg.Lookup(ctx, c.category, c.provider, c.id)
+		if err != nil {
+			t.Errorf("%s %s: %v", c.provider, c.id, err)
+			continue
+		}
+		t.Logf("%s %s → %q | %q | %s | img=%v | desc=%d chars | extra=%v", c.provider, c.id, res.Title, res.Subtitle, res.Year, res.ImageURL != "", len(res.Overview), res.Extra)
+		if c.want != "" && !strings.HasPrefix(res.Title, c.want) {
+			t.Errorf("want %q, got %q", c.want, res.Title)
+		}
+	}
+	if _, err := reg.Lookup(ctx, "album", "deezer", "album:1"); err == nil {
+		t.Log("album:1 unexpectedly exists")
+	} else {
+		t.Logf("missing album → %v", err)
+	}
+	if _, err := reg.Lookup(ctx, "movie", "", ""); err != ErrNoSource {
+		t.Errorf("manual entry: want ErrNoSource, got %v", err)
+	}
+}