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/danmaku_service.go

@@ -369,7 +369,10 @@ func (s *DanmakuService) searchTerms(ctx context.Context, mediaID string) (danma
 	} else if name := strings.TrimSpace(m.Title); name != "" {
 		term.name = name
 	} else {
-		term.name = strings.TrimSuffix(filepath.Base(m.Path), filepath.Ext(m.Path))
+		term.name = mediaSidecarBase(m.Path)
+		if term.name == "" {
+			term.name = strings.TrimSuffix(filepath.Base(m.Path), filepath.Ext(m.Path))
+		}
 	}
 	if m.EpisodeNum > 0 {
 		term.episode = strconv.Itoa(m.EpisodeNum)
@@ -527,23 +530,7 @@ func (s *DanmakuService) hashCachePut(stamp, hash string) {
 // ("xxx.mkv.strm") — so a second strip removes a real video extension only
 // (filepath.Ext would misread names like "xxx.第01话" as having an extension).
 func danmakuMatchFileName(path string) string {
-	if path == "" {
-		return ""
-	}
-	clean := strings.ReplaceAll(path, "\\", "/")
-	if idx := strings.LastIndex(clean, "/"); idx >= 0 {
-		clean = clean[idx+1:]
-	}
-	base := filepath.Base(clean)
-	if ext := filepath.Ext(base); ext != "" {
-		base = strings.TrimSuffix(base, ext)
-	}
-	if second := strings.ToLower(filepath.Ext(base)); second != "" {
-		if _, ok := videoExtensions[second]; ok && second != ".strm" {
-			base = strings.TrimSuffix(base, filepath.Ext(base))
-		}
-	}
-	return strings.TrimSpace(base)
+	return mediaSidecarBase(path)
 }
 
 // mediaHash returns the dandanplay match hash (MD5 of the first 16MB of the