Posters: re-place after a resize, measure cell size without padding, log failed posters

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

internal/ui/cover.go

@@ -8,6 +8,7 @@ import (
 	"image/color"
 	_ "image/jpeg" // poster formats
 	_ "image/png"
+	"net/url"
 	"os/exec"
 	"strings"
 	"time"
@@ -503,6 +504,8 @@ func (a *App) loadCover(ref coverRef, done func(*image.RGBA, error)) {
 			delete(c.waiting, ref.key)
 			if err != nil {
 				c.failed[ref.key] = time.Now()
+				// Say why in the log: a poster that silently never shows up is hard to diagnose.
+				a.logs.add(levelWarn, "Poster not loaded ("+posterSource(ref.key)+"): "+err.Error())
 			} else {
 				if len(c.imgs) >= maxCoverCache {
 					c.imgs = map[string]*image.RGBA{} // simple bound; posters are cheap to fetch again
@@ -518,3 +521,16 @@ func (a *App) loadCover(ref coverRef, done func(*image.RGBA, error)) {
 		})
 	}()
 }
+
+// posterSource describes where a poster key points, for the log: the host and
+// file name of a remote image, or the path on the Radarr/Sonarr instance.
+func posterSource(key string) string {
+	if _, local, ok := strings.Cut(key, "|"); ok {
+		key = local
+	}
+	if u, err := url.Parse(key); err == nil && u.Host != "" {
+		return u.Host + u.Path
+	}
+	path, _, _ := strings.Cut(key, "?")
+	return path
+}