feat(storefront): homepage, module gating, widget protocol, i18n fixes

Storefront homepage & module gating:
- CMS owns storefront GET / (slug="home" with 3-tier resolution)
- Catalog loses GET / (keeps /products only)
- Store root redirect (GET / → /store/dashboard or /store/login)
- Route gating: non-core modules return 404 when disabled for platform
- Seed store default homepages per platform

Widget protocol for customer dashboard:
- StorefrontDashboardCard contract in widgets.py
- Widget aggregator get_storefront_dashboard_cards()
- Orders and Loyalty module widget providers
- Dashboard template renders contributed cards (no module names)

Landing template module-agnostic:
- CTAs driven by storefront_nav (not hardcoded module names)
- Header actions check nav item IDs (not enabled_modules)
- Remove hardcoded "Add Product" sidebar button
- Remove all enabled_modules checks from storefront templates

i18n fixes:
- Title placeholder resolution ({{store_name}}) for store default pages
- Storefront nav label_keys prefixed with module code
- Add storefront.account.* keys to 6 modules (en/fr/de/lb)
- Header/footer CMS pages use get_translated_title(current_language)
- Footer labels use i18n keys instead of hardcoded English

Icon cleanup:
- Standardize on map-pin (remove location-marker alias)
- Replace all location-marker references across templates and docs

Docs:
- Storefront builder vision proposal (6 phases)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/templates/store/partials/sidebar.html

@@ -106,16 +106,6 @@
         </div>
     </div>
 
-    {% if 'catalog' in enabled_modules %}
-    <!-- Quick Actions (static, outside dynamic menu) -->
-    <div class="px-6 my-6">
-        <button class="flex items-center justify-between w-full px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-purple-600 border border-transparent rounded-lg active:bg-purple-600 hover:bg-purple-700 focus:outline-none focus:shadow-outline-purple"
-                @click="$dispatch('open-add-product-modal')">
-            <span x-html="$icon('plus', 'w-4 h-4')"></span>
-            <span class="ml-2">Add Product</span>
-        </button>
-    </div>
-    {% endif %}
 </div>
 {% endmacro %}