feat(admin): separate platform CRUD from CMS, add entity selector macro

- Move platforms menu from CMS to Platform Admin section with create/edit
- Add platform create page, API endpoint, and service method
- Remove CMS-specific content from platform list and detail pages
- Create shared entity_selector + entity_selected_badge Jinja macros
- Create entity-selector.js generalizing store-selector.js for any entity
- Add Tom Select merchant filter to stores page with localStorage persistence
- Migrate store-products page to use shared macros (remove 53 lines of duped CSS)
- Fix broken icons: puzzle→puzzle-piece, building-storefront→store, language→translate, server→cube

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

app/modules/dev_tools/templates/dev_tools/admin/test-stores-users-migration.html

@@ -21,7 +21,7 @@
         </div>
         <div class="flex items-center p-4 bg-white rounded-lg shadow-xs dark:bg-gray-800">
             <div class="p-3 mr-4 text-orange-500 bg-orange-100 rounded-full dark:text-orange-100 dark:bg-orange-500">
-                <span x-html="$icon('building-storefront', 'w-5 h-5')"></span>
+                <span x-html="$icon('store', 'w-5 h-5')"></span>
             </div>
             <div>
                 <p class="mb-2 text-sm font-medium text-gray-600 dark:text-gray-400">Stores List</p>
@@ -53,7 +53,7 @@
         <h4 class="mb-4 text-lg font-semibold text-gray-600 dark:text-gray-300">Quick Actions</h4>
         <div class="flex flex-wrap gap-3">
             <a href="{{ url_for('admin:stores_list') }}" class="flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-orange-600 border border-transparent rounded-lg hover:bg-orange-700 focus:outline-none">
-                <span x-html="$icon('building-storefront', 'w-4 h-4 mr-2')"></span>
+                <span x-html="$icon('store', 'w-4 h-4 mr-2')"></span>
                 Go to Stores List
             </a>
             <a href="{{ url_for('admin:users_list') }}" class="flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-green-600 border border-transparent rounded-lg hover:bg-green-700 focus:outline-none">

app/modules/dev_tools/templates/dev_tools/admin/testing-dashboard.html

@@ -335,7 +335,7 @@
                 <button @click="runTests('tests/integration')"
                         :disabled="running"
                         class="flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-blue-600 border border-transparent rounded-lg hover:bg-blue-700 focus:outline-none disabled:opacity-50 disabled:cursor-not-allowed">
-                    <span x-html="$icon('server', 'w-4 h-4 mr-2')"></span>
+                    <span x-html="$icon('cube', 'w-4 h-4 mr-2')"></span>
                     Run Integration Tests
                 </button>
                 <button @click="collectTests()"