chore: default Cloudron base to 5.0.0; parameterize template with __CLOUDRON_BASE__ and --base option

CloudronPackages/PackageTemplate/Dockerfile

@@ -1,4 +1,4 @@
-FROM cloudron/base:4.2.0
+FROM cloudron/base:__CLOUDRON_BASE__
 
 # Metadata labels (edit as needed)
 LABEL org.opencontainers.image.title="__APP_TITLE__"
@@ -36,4 +36,3 @@ HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
   CMD curl -fsS http://127.0.0.1:${APP_PORT}/ || exit 1
 
 CMD ["/app/pkg/start.sh"]
-

CloudronPackages/PackageTemplate/README.md

@@ -6,6 +6,7 @@ Replace placeholders in files with your app specifics:
 - `__APP_ID__` (e.g., com.example.myapp)
 - `__APP_TITLE__` (human name)
 - `__HTTP_PORT__` (default internal app port)
+- `__CLOUDRON_BASE__` (Cloudron base image tag, e.g., 5.0.0)
 
 Files
 - `CloudronManifest.json` – base manifest
@@ -21,4 +22,3 @@ Usage
    `scripts/new-package.sh MyApp --id com.example.myapp --title "My App" --port 3000`
 2. Adjust Dockerfile and start.sh to run your app.
 3. Build and test locally; then commit and push.
-