Add full cross-platform path support

- Added automatic volume path translation in deployment (deploy.js)
- Updated FileBrowser template to use /opt/ instead of hard-coded E:/
- Migrated self-updater.js to use centralized platformPaths module
- Updated UI placeholders to use platform-neutral paths (/media/)
- All paths now automatically adapt to Windows or Linux at runtime via process.platform detection

dashcaddy-api/app-templates.js

@@ -672,8 +672,8 @@ const APP_TEMPLATES = {
       image: "filebrowser/filebrowser:latest",
       ports: ["{{PORT}}:80"],
       volumes: [
-        "E:/docker-progs/filebrowser/data:/srv",
-        "E:/docker-progs/filebrowser/database:/database"
+        "/opt/filebrowser/data:/srv",
+        "/opt/filebrowser/database:/database"
       ],
       environment: {}
     },