fix: replace inline SVGs with $icon() helper (FE-002)

Convert 90 inline SVG icons to use the shared $icon() helper function
across shop and vendor templates for consistency and maintainability.

Templates updated:
- Shop: checkout, products, login, register, forgot/reset-password
- Shop account: addresses, dashboard, messages, order-detail, orders, profile
- Vendor: billing, login, onboarding, team, landing pages (4 variants)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/templates/vendor/login.html

@@ -88,10 +88,7 @@
                                         class="block w-full px-4 py-2 mt-4 text-sm font-medium leading-5 text-center 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 disabled:opacity-50 disabled:cursor-not-allowed">
                                     <span x-show="!loading">Sign in</span>
                                     <span x-show="loading" class="flex items-center justify-center">
-                                        <svg class="inline w-4 h-4 mr-2 animate-spin" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
-                                            <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
-                                            <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
-                                        </svg>
+                                        <span class="inline w-4 h-4 mr-2" x-html="$icon('spinner', 'w-4 h-4 animate-spin')"></span>
                                         Signing in...
                                     </span>
                                 </button>
@@ -116,10 +113,7 @@
 
                         <!-- Loading State -->
                         <div x-show="loading && !vendor" class="text-center py-8">
-                            <svg class="inline w-8 h-8 animate-spin text-purple-600" xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 24 24">
-                                <circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
-                                <path class="opacity-75" fill="currentColor" d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"></path>
-                            </svg>
+                            <span class="inline-block w-8 h-8 text-purple-600" x-html="$icon('spinner', 'w-8 h-8 animate-spin')"></span>
                             <p class="mt-2 text-sm text-gray-600 dark:text-gray-400">Loading vendor information...</p>
                         </div>