feat: add artist image uploads and image-folder artwork source (#5198)

* feat: add shared ImageUploadService for entity image management

* feat: add UploadedImage field and methods to Artist model

* feat: add uploaded_image column to artist table

* feat: add ArtistImageFolder config option

* refactor: wire ImageUploadService and delegate playlist file ops to it

Wire ImageUploadService into the DI container and refactor the playlist
service to delegate image file operations (SetImage/RemoveImage) to the
shared ImageUploadService, removing duplicated file I/O logic. A local
ImageUploadService interface is defined in core/playlists to avoid an
import cycle between core and core/playlists.

* feat: artist artwork reader checks uploaded image first

* feat: add image-folder priority source for artist artwork

* feat: cache key invalidation for image-folder and uploaded images

* refactor: extract shared image upload HTTP helpers

* feat: add artist image upload/delete API endpoints

* refactor: playlist handlers use shared image upload helpers

* feat: add shared ImageUploadOverlay component

* feat: add i18n keys for artist image upload

* feat: add image upload overlay to artist detail pages

* refactor: playlist details uses shared ImageUploadOverlay component

* fix: add gosec nolint directive for ParseMultipartForm

* refactor: deduplicate image upload code and optimize dir scanning

- Remove dead ImageFilename methods from Artist and Playlist models
  (production code uses core.imageFilename exclusively)
- Extract shared uploadedImagePath helper in model/image.go
- Extract findImageInArtistFolder to deduplicate dir-scanning logic
  between fromArtistImageFolder and getArtistImageFolderModTime
- Fix fileInputRef in useCallback dependency array

* fix: include artist UpdatedAt in artwork cache key

Without this, uploading or deleting an artist image would not
invalidate the cached artwork because the cache key was only based
on album folder timestamps, not the artist's own UpdatedAt field.

* feat: add Portuguese translations for artist image upload

* refactor: use shared i18n keys for cover art upload messages

Move cover art upload/remove translations from per-entity sections
(artist, playlist) to a shared top-level "message" section, avoiding
duplication across entity types and translation files.

* refactor: move cover art i18n keys to shared message section for all languages

* refactor: simplify image upload code and eliminate redundancies

Extracted duplicate image loading/lightbox state logic from
DesktopArtistDetails and MobileArtistDetails into a shared
useArtistImageState hook. Moved entity type constants to the consts
package and replaced raw string literals throughout model, core, and
nativeapi packages. Exported model.UploadedImagePath and reused it in
core/image_upload.go to consolidate path construction. Cached the
ArtistImageFolder lookup result in artistReader to eliminate a redundant
os.ReadDir call on every artwork request.

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

* style: fix prettier formatting in ImageUploadOverlay

* fix: address code review feedback on image upload error handling

- RemoveImage now returns errors instead of swallowing them
- Artist handlers distinguish not-found from other DB errors
- Defer multipart temp file cleanup after parsing

* fix: enforce hard request size limit with MaxBytesReader for image uploads

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

---------

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

resources/i18n/zh-Hant.json

@@ -219,19 +219,13 @@
         "saveQueue": "將播放佇列儲存到播放清單",
         "searchOrCreate": "搜尋播放清單，或輸入名稱來新建…",
         "pressEnterToCreate": "按 Enter 鍵建立新的播放清單",
-        "removeFromSelection": "移除選取項目",
-        "uploadCover": "上傳封面",
-        "removeCover": "移除封面"
+        "removeFromSelection": "移除選取項目"
       },
       "message": {
         "duplicate_song": "加入重複的歌曲",
         "song_exist": "有重複歌曲正要加入播放清單，您要加入或略過重複歌曲？",
         "noPlaylistsFound": "找不到播放清單",
-        "noPlaylists": "暫無播放清單",
-        "coverUploaded": "已更新封面圖",
-        "coverRemoved": "已移除封面圖",
-        "coverUploadError": "上傳封面圖時發生錯誤",
-        "coverRemoveError": "移除封面圖時發生錯誤"
+        "noPlaylists": "暫無播放清單"
       }
     },
     "radio": {
@@ -597,7 +591,13 @@
     "remove_all_missing_content": "您確定要從媒體庫中刪除所有遺失的檔案嗎？這將永久刪除它們的所有相關資訊，包括它們的播放次數和評分。",
     "noSimilarSongsFound": "找不到相似歌曲",
     "noTopSongsFound": "找不到熱門歌曲",
-    "startingInstantMix": "正在載入即時混音..."
+    "startingInstantMix": "正在載入即時混音...",
+    "uploadCover": "上傳封面",
+    "removeCover": "移除封面",
+    "coverUploaded": "已更新封面圖",
+    "coverRemoved": "已移除封面圖",
+    "coverUploadError": "上傳封面圖時發生錯誤",
+    "coverRemoveError": "移除封面圖時發生錯誤"
   },
   "menu": {
     "library": "媒體庫",
@@ -718,4 +718,4 @@
     "empty": "無播放內容",
     "minutesAgo": "1 分鐘前 |||| %{smart_count} 分鐘前"
   }
-}
+}