Create docker-transmission-openvpn application (#866)

* Create docker-transmission-openvpn application

* Partially addressed review 1

* Fix: Avoid .env generation error

* Add execute right on image scripts

* Fix: Force transmission home var

* Fix: unsupported custom app path

* Review: Make .env generation simpler

* Fix: Change cron command causing error due to crlf

* Review: Rework fetching WebUI

* Improve cleaning up

* Add warning message to setup vpn provider

* Rework update function

* Fix: Change var_tun default value to yes

* Review: Remove Healthcheck cron job

* Review: Directly deploy WebUI to /opt/transmission-ui/

* Make custom config persistent when updating

* Fix: fetch WebUI from correct URL (old one was invalid)

* Fix: resolve conflicting Privoxy instance

* Fix: align binary path when fetching branch vs release

* Security: Remove old and deprecated WebUI for security reasons

* Review: drop unnecessary packages and optimize implementations

* Review: Implement local network dynamic detection

* CR, OS: Migrate to Debian 13

* Use quiet mode for several commands as recommended

* Review: Replace hard coding app name instead of using var $APP

* Review: Reduce amount of msg_blocks

* refactor

* refactor

---------

Co-authored-by: Tobias <96661824+CrazyWolf13@users.noreply.github.com>

frontend/public/json/transmission-openvpn.json

@@ -0,0 +1,40 @@
+{
+  "name": "Transmission-Openvpn",
+  "slug": "transmission-openvpn",
+  "categories": [
+    11
+  ],
+  "date_created": "2025-09-04",
+  "type": "ct",
+  "updateable": true,
+  "privileged": false,
+  "interface_port": 9091,
+  "documentation": "https://haugene.github.io/docker-transmission-openvpn/",
+  "config_path": "/opt/transmission-openvpn/",
+  "website": "https://github.com/haugene/docker-transmission-openvpn",
+  "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons/webp/transmission.webp",
+  "description": "This project runs Transmission + OpenVPN natively in an LXC container, using the popular docker-transmission-openvpn image as a base. It ensures all torrent traffic is securely routed through a VPN tunnel, supports a wide range of VPN providers, and offers flexible configuration options",
+  "install_methods": [
+    {
+      "type": "default",
+      "script": "ct/transmission-openvpn.sh",
+      "resources": {
+        "cpu": 1,
+        "ram": 512,
+        "hdd": 8,
+        "os": "Debian",
+        "version": "13"
+      }
+    }
+  ],
+  "default_credentials": {
+    "username": null,
+    "password": null
+  },
+  "notes": [
+    {
+      "text": "This application requires a VPN provider to work. Please refer to your VPN provider’s documentation for setting up OpenVPN.",
+      "type": "warning"
+    }
+  ]
+}