feat(ui): add cover art support for internet radio stations (#5229)

* feat(artwork): add KindRadioArtwork and EntityRadio constant

* feat(model): add UploadedImage field and artwork methods to Radio

* feat(model): add Radio to GetEntityByID lookup chain

* feat(db): add uploaded_image column to radio table

* feat(artwork): add radio artwork reader with uploaded image fallback

* feat(api): add radio image upload/delete endpoints

* feat(ui): add radio artwork ID prefix to getCoverArtUrl

* feat(ui): add cover art display and upload to RadioEdit

* feat(ui): add cover art thumbnails to radio list

* feat(ui): prefer artwork URL in radio player helper

* refactor: remove redundant code in radio artwork

- Remove duplicate Avatar rendering in RadioList by reusing CoverArtField
- Remove redundant UpdatedAt assignment in radio image handlers (already set by repository Put)

* refactor(ui): extract shared useImageLoadingState hook

Move image loading/error/lightbox state management into a shared
useImageLoadingState hook in common/. Consolidates duplicated logic
from AlbumDetails, PlaylistDetails, RadioEdit, and artist detail views.

* feat(ui): use radio placeholder icon when no uploaded image

Remove album placeholder fallback from radio artwork reader so radios
without an uploaded image return ErrUnavailable. On the frontend, show
the internet-radio-icon.svg placeholder instead of requesting server
artwork when no image is uploaded, allowing favicon fallback in the
player.

* refactor(ui): update defaultOff fields in useSelectedFields for RadioList

Signed-off-by: Deluan <deluan@navidrome.org>

* fix: address code review feedback

- Add missing alt attribute to CardMedia in RadioEdit for accessibility
- Fix UpdateInternetRadio to preserve UploadedImage field by fetching
  existing radio before updating (prevents Subsonic API from clearing
  custom artwork)
- Add Reader() level tests to verify ErrUnavailable is returned when
  radio has no uploaded image

* refactor: add colsToUpdate to RadioRepository.Put

Use the base sqlRepository.put with column filtering instead of
hand-rolled SQL. UpdateInternetRadio now specifies only the Subsonic API
fields, preventing UploadedImage from being cleared. Image upload/delete
handlers specify only UploadedImage.

* fix: ensure UpdatedAt is included in colsToUpdate for radio Put

---------

Signed-off-by: Deluan <deluan@navidrome.org>

db/migrations/20260318182414_add_radio_uploaded_image.go

@@ -0,0 +1,22 @@
+package migrations
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/pressly/goose/v3"
+)
+
+func init() {
+	goose.AddMigrationContext(upAddRadioUploadedImage, downAddRadioUploadedImage)
+}
+
+func upAddRadioUploadedImage(ctx context.Context, tx *sql.Tx) error {
+	_, err := tx.ExecContext(ctx, `ALTER TABLE radio ADD COLUMN uploaded_image VARCHAR(255) NOT NULL DEFAULT ''`)
+	return err
+}
+
+func downAddRadioUploadedImage(ctx context.Context, tx *sql.Tx) error {
+	// This code is executed when the migration is rolled back.
+	return nil
+}