fix: resolve homepage sections editor and rendering issues

- Fix sections editor not showing by converting isHomepage getter to property
- Add Alpine Collapse plugin for accordion animations
- Fix Quill editor content not syncing after page load
- Add platform dropdown to content page edit form
- Create shared templates config (app/templates_config.py) with i18n globals
  to make _() translation function available in Jinja2 macros
- Fix pricing template field names (monthly_price → price_monthly)
- Fix translation key (pricing.save_20 → pricing.save_months)
- Add tiers context to CMS homepage route for pricing section
- Fix architecture validation issues (language defaults, inline SVGs → $icon)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/templates/admin/base.html

@@ -130,7 +130,10 @@
     <!-- 7. SEVENTH: Vendor Selector (depends on Tom Select and API Client) -->
     <script src="{{ url_for('static', path='shared/js/vendor-selector.js') }}"></script>
 
-    <!-- 8. EIGHTH: Alpine.js v3 with CDN fallback (with defer) -->
+    <!-- 8a. Alpine.js Collapse Plugin (must load before Alpine) -->
+    <script defer src="https://cdn.jsdelivr.net/npm/@alpinejs/collapse@3.13.3/dist/cdn.min.js"></script>
+
+    <!-- 8b. Alpine.js v3 with CDN fallback (with defer) -->
     <script>
     (function() {
         var script = document.createElement('script');