feat(mediaserver): Plex/Jellyfin/Emby auto-refresh + .strm instant mode

Sprint 1 — Auto-refresh after download:
- New [[mediaserver]] TOML section with kind/url/token/sections
- mediaserver.Refresh() fans out to Plex (partial via section ID auto-mapping
  from file path prefix) and Jellyfin/Emby (full library scan)
- Manager.OnFinalized callback wired in daemon to trigger refresh after
  organize() completes — keeps engine package free of mediaserver dep
- New unarr mediaserver {setup,list,remove,test} commands
- unarr init wizard offers to configure refresh when a server is detected

Sprint 2 — .strm instant mode (cloud + agent):
- Mode strm-to-library handled in daemon dispatch: writes a one-line .strm
  file pointing to the cloud-resolved debrid HTTPS URL, then triggers refresh
- engine.WriteStrm + StrmDestForTask mirror organize()'s naming so Plex/Jellyfin
  see the expected folder structure (Movies/Title (Year)/, TV Shows/Show/Season XX/)
- Atomic write (temp + rename) so partial files never get indexed
- Reports completed/failed status to the cloud via existing agent client

internal/config/config.go

@@ -9,18 +9,20 @@ import (
 	"strings"
 
 	"github.com/BurntSushi/toml"
+	"github.com/torrentclaw/unarr/internal/mediaserver"
 )
 
 // Config holds all persistent CLI configuration.
 type Config struct {
-	Auth          AuthConfig          `toml:"auth"`
-	Agent         AgentConfig         `toml:"agent"`
-	Download      DownloadConfig      `toml:"downloads"`
-	Organize      OrganizeConfig      `toml:"organize"`
-	Daemon        DaemonConfig        `toml:"daemon"`
-	Notifications NotificationsConfig `toml:"notifications"`
-	General       GeneralConfig       `toml:"general"`
-	Library       LibraryConfig       `toml:"library"`
+	Auth          AuthConfig                 `toml:"auth"`
+	Agent         AgentConfig                `toml:"agent"`
+	Download      DownloadConfig             `toml:"downloads"`
+	Organize      OrganizeConfig             `toml:"organize"`
+	Daemon        DaemonConfig               `toml:"daemon"`
+	Notifications NotificationsConfig        `toml:"notifications"`
+	General       GeneralConfig              `toml:"general"`
+	Library       LibraryConfig              `toml:"library"`
+	MediaServers  []mediaserver.ServerConfig `toml:"mediaserver"`
 }
 
 type AuthConfig struct {