Add minify build script and generate .min CSS/JS; rename position to brand-aside

Build tooling:
- Add package.json with clean-css and terser dev dependencies
- Add scripts/minify.js: reads joomla.asset.json, auto-detects source/.min
  pairs, and minifies all template-owned CSS and JS files
- Add node_modules/ to .gitignore

Generated .min files (all 6 manifest pairs):
- css/template.min.css      (17.8% saved)
- css/editor.min.css        (49.4% saved)
- css/theme/light.standard.min.css  (13.1% saved)
- css/theme/dark.standard.min.css   (14.4% saved)
- js/template.min.js        (58.2% saved)
- js/gtm.min.js             (62.3% saved)

Rename: header-aside → brand-aside (position, CSS class, language keys)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/media/css/template.css

@@ -14385,7 +14385,7 @@ fieldset>* {
 	width: 100%;
 }
 
-.container-header-aside {
+.container-brand-aside {
 	margin-inline-start: auto;
 	display: flex;
 	align-items: center;