feat: add migrate command, media server detection, and debrid auto-config

- Migration wizard from Sonarr/Radarr/Prowlarr (unarr migrate) [pre-beta]
  - Auto-detect instances via Docker, config files, port scan, Prowlarr
  - Import wanted list (monitored+missing movies/series)
  - Import download history and blocklist to avoid re-downloading
  - Extract debrid tokens from *arr download clients
  - Quality profile mapping to preferred_quality config
  - DISTINCT ON PostgreSQL query for optimal torrent selection
  - JSON export with --dry-run --json (text to stderr, JSON to stdout)
- Media server detection (Plex/Jellyfin/Emby) in unarr init
  - Detects library paths and offers them as download directory options
- Debrid auto-configuration in unarr init
  - Scans *arr instances for debrid tokens
  - Validates and saves via API if user confirms
- New preferred_quality setting in config (2160p/1080p/720p)
- Library scan command (unarr scan) with ffprobe metadata extraction

internal/agent/client.go

@@ -153,6 +153,33 @@ func (c *Client) GetUsenetUsage(ctx context.Context) (*UsenetUsageResponse, erro
 	return &resp, nil
 }
 
+// ConfigureDebrid saves a debrid provider token for the user (used by unarr init/migrate).
+func (c *Client) ConfigureDebrid(ctx context.Context, req ConfigureDebridRequest) (*ConfigureDebridResponse, error) {
+	var resp ConfigureDebridResponse
+	if err := c.doPost(ctx, "/api/internal/agent/debrid-config", req, &resp); err != nil {
+		return nil, fmt.Errorf("configure debrid: %w", err)
+	}
+	return &resp, nil
+}
+
+// BatchDownload queues multiple items for download (used by unarr migrate).
+func (c *Client) BatchDownload(ctx context.Context, req BatchDownloadRequest) (*BatchDownloadResponse, error) {
+	var resp BatchDownloadResponse
+	if err := c.doPost(ctx, "/api/internal/agent/batch-download", req, &resp); err != nil {
+		return nil, fmt.Errorf("batch download: %w", err)
+	}
+	return &resp, nil
+}
+
+// SyncLibrary sends scanned library items to the server for matching and upgrade discovery.
+func (c *Client) SyncLibrary(ctx context.Context, req LibrarySyncRequest) (*LibrarySyncResponse, error) {
+	var resp LibrarySyncResponse
+	if err := c.doPost(ctx, "/api/internal/agent/library-sync", req, &resp); err != nil {
+		return nil, fmt.Errorf("library sync: %w", err)
+	}
+	return &resp, nil
+}
+
 // doPost sends a JSON POST request and decodes the response.
 func (c *Client) doPost(ctx context.Context, path string, body any, dst any) error {
 	jsonBody, err := json.Marshal(body)