feat(strm): 同名多版本择优 / keep_ext，并支持合并展示与播放切换 (#30)

* feat(strm): 同名多版本择优/keep_ext，并支持合并展示与播放切换

默认对同名不同扩展（如 .mkv/.mp4）按体积→mtime→扩展名优先级择优生成一条 strm，冲突打日志；开启 keep_ext 则分别生成 name.ext.strm。媒体详情与播放器可切换版本，列表继续合并同片多版本，Emby MediaSources 名称区分容器/分辨率。

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* fix(meta): 边车匹配忽略 .mkv.strm 中间扩展，同片共享 NFO/海报/字幕

NFO、海报、字幕与刮削写出统一使用 mediaSidecarBase 词干，使竞女01.mkv.strm
与竞女01.mp4.strm 配对同一套 竞女01.nfo / 竞女01-poster / 竞女01.srt；
仍兼容历史上的 name.mkv.nfo 命名。

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* fix(emby): People NFO 按共享词干匹配 keep_ext strm

resolveMediaPeople 改为查找竞女01.nfo（并兼容旧的竞女01.mkv.nfo），
同时修正把 decodeNFOFile 的 partial 误当 ok 导致完整 NFO 被跳过的问题。

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

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Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

internal/service/local_metadata_artwork.go

@@ -54,39 +54,59 @@ func mergeArtworkMetadata(meta *LocalMetadata, mediaPath, showBaseDir string) {
 }
 
 func localPosterCandidates(mediaPath string) []string {
-	base := strings.TrimSuffix(filepath.Base(mediaPath), filepath.Ext(mediaPath))
-	names := []string{
-		base + "-poster",
-		base + ".poster",
-		"poster",
-		"folder",
-		"cover",
-		"movie",
-		"show",
-		base + "-cover",
-		base + ".cover",
-		base,
-		base + "-thumb",
-		base + ".thumb",
-		"thumb",
+	names := make([]string, 0, 24)
+	seen := map[string]struct{}{}
+	add := func(name string) {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			return
+		}
+		key := strings.ToLower(name)
+		if _, ok := seen[key]; ok {
+			return
+		}
+		seen[key] = struct{}{}
+		names = append(names, name)
+	}
+	for _, base := range mediaSidecarBaseVariants(mediaPath) {
+		add(base + "-poster")
+		add(base + ".poster")
+		add(base + "-cover")
+		add(base + ".cover")
+		add(base)
+		add(base + "-thumb")
+		add(base + ".thumb")
+	}
+	for _, name := range []string{"poster", "folder", "cover", "movie", "show", "thumb"} {
+		add(name)
 	}
 	return append(adultArtworkNameCandidates(mediaPath, "poster"), names...)
 }
 
 func localBackdropCandidates(mediaPath string) []string {
-	base := strings.TrimSuffix(filepath.Base(mediaPath), filepath.Ext(mediaPath))
-	names := []string{
-		base + "-fanart",
-		base + ".fanart",
-		base + "-backdrop",
-		base + ".backdrop",
-		base + "-background",
-		"fanart",
-		"backdrop",
-		"background",
-		"landscape",
-		"banner",
-		"clearart",
+	names := make([]string, 0, 24)
+	seen := map[string]struct{}{}
+	add := func(name string) {
+		name = strings.TrimSpace(name)
+		if name == "" {
+			return
+		}
+		key := strings.ToLower(name)
+		if _, ok := seen[key]; ok {
+			return
+		}
+		seen[key] = struct{}{}
+		names = append(names, name)
+	}
+	for _, base := range mediaSidecarBaseVariants(mediaPath) {
+		add(base + "-fanart")
+		add(base + ".fanart")
+		add(base + "-backdrop")
+		add(base + ".backdrop")
+		add(base + "-background")
+	}
+	for _, name := range []string{"fanart", "backdrop", "background", "landscape", "banner", "clearart"} {
+		add(name)
 	}
 	return append(adultArtworkNameCandidates(mediaPath, "backdrop"), names...)
 }