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/tvdb.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"strconv"
 	"sync"
 	"time"
 )
@@ -79,19 +80,8 @@ func (t *tvdb) Search(ctx context.Context, query string) ([]Result, error) {
 		} `json:"data"`
 	}
 	u := "https://api4.thetvdb.com/v4/search?" + url.Values{"query": {query}, "type": {"series"}, "limit": {"20"}}.Encode()
-	for attempt := 0; ; attempt++ {
-		tok, err := t.token(ctx, attempt > 0)
-		if err != nil {
-			return nil, err
-		}
-		err = t.r.getJSON(ctx, u, map[string]string{"Authorization": "Bearer " + tok}, &resp)
-		if isStatus(err, 401) && attempt == 0 {
-			continue
-		}
-		if err != nil {
-			return nil, err
-		}
-		break
+	if err := t.get(ctx, u, &resp); err != nil {
+		return nil, err
 	}
 	out := make([]Result, 0, len(resp.Data))
 	for _, s := range resp.Data {
@@ -128,3 +118,81 @@ func (t *tvdb) Search(ctx context.Context, query string) ([]Result, error) {
 	}
 	return out, nil
 }
+
+// get calls the API with a token, logging in again once if it expired.
+func (t *tvdb) get(ctx context.Context, u string, out any) error {
+	for attempt := 0; ; attempt++ {
+		tok, err := t.token(ctx, attempt > 0)
+		if err != nil {
+			return err
+		}
+		err = t.r.getJSON(ctx, u, map[string]string{"Authorization": "Bearer " + tok}, out)
+		if isStatus(err, 401) && attempt == 0 {
+			continue
+		}
+		return err
+	}
+}
+
+// Lookup refreshes one series by its TheTVDB ID, preferring English titles
+// and overviews.
+func (t *tvdb) Lookup(ctx context.Context, providerID string) (Result, error) {
+	if _, err := strconv.ParseInt(providerID, 10, 64); err != nil {
+		return Result{}, ErrGone
+	}
+	var s struct {
+		Data struct {
+			Name            string `json:"name"`
+			Slug            string `json:"slug"`
+			Image           string `json:"image"`
+			Year            string `json:"year"`
+			FirstAired      string `json:"firstAired"`
+			Overview        string `json:"overview"`
+			OriginalNetwork struct {
+				Name string `json:"name"`
+			} `json:"originalNetwork"`
+			LatestNetwork struct {
+				Name string `json:"name"`
+			} `json:"latestNetwork"`
+		} `json:"data"`
+	}
+	err := t.get(ctx, "https://api4.thetvdb.com/v4/series/"+providerID+"/extended?short=true", &s)
+	if isStatus(err, 404) {
+		return Result{}, ErrGone
+	}
+	if err != nil {
+		return Result{}, err
+	}
+	d := s.Data
+	res := Result{
+		Provider:    "tvdb",
+		ProviderID:  providerID,
+		Title:       d.Name,
+		Subtitle:    d.OriginalNetwork.Name,
+		Year:        d.Year,
+		ImageURL:    d.Image,
+		ExternalURL: "https://thetvdb.com/series/" + d.Slug,
+		Overview:    truncate(d.Overview, maxDescription),
+	}
+	if res.Subtitle == "" {
+		res.Subtitle = d.LatestNetwork.Name
+	}
+	if res.Year == "" {
+		res.Year = yearOf(d.FirstAired)
+	}
+	var eng struct {
+		Data struct {
+			Name     string `json:"name"`
+			Overview string `json:"overview"`
+		} `json:"data"`
+	}
+	if err := t.get(ctx, "https://api4.thetvdb.com/v4/series/"+providerID+"/translations/eng", &eng); err == nil {
+		if eng.Data.Name != "" {
+			res.Title = eng.Data.Name
+		}
+		if eng.Data.Overview != "" {
+			res.Overview = truncate(eng.Data.Overview, maxDescription)
+		}
+	}
+	return res, nil
+}