feat(organize/scan): transfer modes, seeding-safe relocation, inode dedup, incremental scanning

- Organizer: add move/copy/hardlink/symlink transfer modes (default move),
  per-request target_path/transfer_mode overrides, and honor organize.target_dir
  / organize.transfer_mode settings.
- keep_seeding (default on): escalate move->hardlink (cross-device->copy) so the
  qBittorrent source stays in place and continues seeding after organize.
- qBittorrent SetLocation + POST /downloads/relocate to migrate whole torrents
  while keeping them seeding.
- Scanner: FileID (device:inode) hardlink dedup to avoid duplicate recognition
  and double-counted storage; extract single-file ingest.
- Watcher: recursive watch + incremental per-file ingest/remove instead of full
  re-scan; periodic full library scan now gated behind scan.periodic_enabled
  (default off) to reduce disk wear.
- Telegram bot: handle callback_query in polling, declare allowed_updates in
  webhook, answer callbacks.
- Frontend: settings for transfer mode / keep_seeding / periodic scan; organize
  panel target dir + transfer mode overrides.
- Tests for transfer modes, organizer resolution, SetLocation, inode dedup,
  incremental ingest/remove.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

internal/handler/downloads.go

@@ -190,6 +190,28 @@ func deleteDownloadHandler(svc *service.Container) gin.HandlerFunc {
 	}
 }
 
+type relocateDownloadReq struct {
+	Hash     string `json:"hash" binding:"required"`
+	Location string `json:"location" binding:"required"`
+}
+
+// relocateDownloadHandler moves a torrent's data to a new directory while
+// keeping it seeding (qBittorrent setLocation).
+func relocateDownloadHandler(svc *service.Container) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		var req relocateDownloadReq
+		if err := c.ShouldBindJSON(&req); err != nil {
+			c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
+			return
+		}
+		if err := svc.Downloads.RelocateTorrent(c.Request.Context(), req.Hash, req.Location); err != nil {
+			c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, gin.H{"hash": strings.TrimSpace(req.Hash), "location": strings.TrimSpace(req.Location)})
+	}
+}
+
 func reloadDownloadConfigHandler(svc *service.Container) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		if err := svc.Downloads.ReloadConfig(c.Request.Context()); err != nil {