Add install and setup scripts for multiple Linux distros

Introduces container setup scripts and install scripts for AlmaLinux, CentOS Stream, Devuan, Fedora, Gentoo, openEuler, openSUSE, Rocky Linux, and updates Alpine install script. Adds corresponding JSON metadata files for each distribution in the frontend. These changes enable streamlined LXC container creation and installation for a wide range of Linux distributions.

frontend/public/json/gentoo.json

@@ -0,0 +1,38 @@
+{
+  "name": "Gentoo",
+  "slug": "gentoo",
+  "categories": [0],
+  "date_created": "2025-12-04",
+  "type": "ct",
+  "updateable": true,
+  "privileged": false,
+  "interface_port": null,
+  "documentation": "https://wiki.gentoo.org/",
+  "website": "https://www.gentoo.org/",
+  "logo": "https://cdn.jsdelivr.net/gh/selfhst/icons/webp/gentoo.webp",
+  "config_path": "",
+  "description": "Gentoo is a highly customizable source-based Linux distribution. Users compile software optimized for their specific hardware.",
+  "install_methods": [
+    {
+      "type": "default",
+      "script": "ct/gentoo.sh",
+      "resources": {
+        "cpu": 2,
+        "ram": 1024,
+        "hdd": 8,
+        "os": "gentoo",
+        "version": "current"
+      }
+    }
+  ],
+  "default_credentials": {
+    "username": "root",
+    "password": null
+  },
+  "notes": [
+    {
+      "text": "Gentoo compiles packages from source. Initial setup may take time.",
+      "type": "warning"
+    }
+  ]
+}