feat: Add final stacks (Batch 3)

Added stacks:
- plex (Media server)
- pterodactyl-panel (Game server management)
- gotosocial (ActivityPub/Fediverse)
- backrest (Backup UI)

All stacks include:
- compose.yml with proper configuration
- README.md with deployment info
- stack.toml for Komodo Resource Sync

TOTAL: 21 stacks ready for Komodo deployment!

stacks/backrest/README.md

@@ -0,0 +1,24 @@
+# Backrest
+
+💾 Backup Management UI
+
+## Deploy in Komodo
+
+**Pfad:** `stacks/backrest/`
+
+## Ports
+
+- `8080` - Web UI
+
+## Caddy
+
+```caddyfile
+backup.example.com {
+    reverse_proxy localhost:8080
+}
+```
+
+## Notes
+
+- UI für Restic Backups
+- Backup-Pfad anpassen