Trakt lists: keep the Radarr/Sonarr lookups of their titles on disk

Library membership is asked every time via movie?tmdbId= / series?tvdbId=;
only the lookups of titles not in the library are stored (3 days).

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

internal/ui/diskcache.go

@@ -169,6 +169,42 @@ func (d *diskCache) savePeople(all map[string]savedPeople) error {
 	return writeAtomic(d.peoplePath(), data)
 }
 
+func (d *diskCache) lookupsPath() string { return filepath.Join(d.dir, "lookups.json") }
+
+// loadLookups reads the stored Radarr/Sonarr lookups that are not too old.
+func (d *diskCache) loadLookups() map[string]savedLookup {
+	out := map[string]savedLookup{}
+	if d.dir == "" {
+		return out
+	}
+	data, err := os.ReadFile(d.lookupsPath())
+	if err != nil {
+		return out
+	}
+	var all map[string]savedLookup
+	if json.Unmarshal(data, &all) != nil {
+		return out // unreadable: start afresh, it is only a cache
+	}
+	for k, l := range all {
+		if time.Since(l.Saved) <= lookupTTL {
+			out[k] = l
+		}
+	}
+	return out
+}
+
+// saveLookups writes the lookups.
+func (d *diskCache) saveLookups(all map[string]savedLookup) error {
+	if d.dir == "" {
+		return nil
+	}
+	data, err := json.Marshal(all)
+	if err != nil {
+		return err
+	}
+	return writeAtomic(d.lookupsPath(), data)
+}
+
 // writeAtomic writes a file through a temporary file and a rename, creating
 // the directory (private) if needed.
 func writeAtomic(path string, data []byte) error {