feat: add episode titles api endpoint

internal/playback/handler/handler.go

@@ -40,12 +40,46 @@ func (h *PlaybackHandler) Register(r *gin.Engine) {
 	r.GET("/anime/:id/watch", h.HandleWatchPage)
 	r.POST("/api/watch-progress", h.HandleSaveProgress)
 	r.POST("/api/watch-complete", h.HandleWatchComplete)
+	r.GET("/api/watch/episodes/:animeId/titles", h.HandleEpisodeTitles)
 	r.GET("/api/watch/episode/:animeId/:episode", h.HandleEpisodeData)
 	r.POST("/api/watch/segments", h.HandleUpsertSkipSegment)
 	r.GET("/watch/proxy/stream", h.HandleProxyStream)
 	r.GET("/watch/proxy/subtitle", h.HandleProxySubtitle)
 }
 
+func (h *PlaybackHandler) HandleEpisodeTitles(c *gin.Context) {
+	animeID, err := strconv.Atoi(c.Param("animeId"))
+	if err != nil || animeID <= 0 {
+		server.RespondHTMLOrJSONError(c, http.StatusBadRequest, "invalid anime id")
+		return
+	}
+
+	enricher, ok := h.svc.(domain.PlaybackEpisodeTitleService)
+	if !ok {
+		server.RespondHTMLOrJSONError(c, http.StatusServiceUnavailable, "episode titles are unavailable")
+		return
+	}
+	episodes, err := enricher.EnrichEpisodeTitles(c.Request.Context(), animeID)
+	if err != nil {
+		server.RespondError(
+			c,
+			http.StatusBadGateway,
+			"watch_episode_titles_failed",
+			"playback",
+			"episode titles are unavailable",
+			map[string]any{"anime_id": animeID},
+			err,
+		)
+		return
+	}
+
+	titles := make([]gin.H, 0, len(episodes))
+	for _, episode := range episodes {
+		titles = append(titles, gin.H{"number": episode.Number, "title": episode.Title})
+	}
+	c.JSON(http.StatusOK, titles)
+}
+
 func (h *PlaybackHandler) HandleWatchPage(c *gin.Context) {
 	id, err := strconv.Atoi(c.Param("id"))
 	if err != nil || id <= 0 {