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/index.php

@@ -390,9 +390,9 @@ $wa->useScript('user.js');         // js/user.js
 						</div>
 					<?php endif; ?>
 				</div>
-				<?php if ($this->countModules('header-aside', true)) : ?>
-					<div class="container-header-aside">
-						<jdoc:include type="modules" name="header-aside" style="none" />
+				<?php if ($this->countModules('brand-aside', true)) : ?>
+					<div class="container-brand-aside">
+						<jdoc:include type="modules" name="brand-aside" style="none" />
 					</div>
 				<?php endif; ?>
 			</div>