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/pterodactyl-panel/README.md

@@ -0,0 +1,25 @@
+# Pterodactyl Panel
+
+🎮 Game Server Management
+
+## Deploy in Komodo
+
+**Pfad:** `stacks/pterodactyl-panel/`
+
+## Ports
+
+- `8080` - HTTP
+- `8443` - HTTPS
+
+## Caddy
+
+```caddyfile
+panel.example.com {
+    reverse_proxy localhost:8080
+}
+```
+
+## Notes
+
+- Komplexes Setup mit MariaDB + Redis
+- Benötigt Pterodactyl Wings auf Game-Servern