fix: loyalty module end-to-end — merchant route, store menus, sidebar, API error handling

- Add merchant loyalty overview route and template (was 404)
- Fix store loyalty route paths to match menu URLs (/{store_code}/loyalty/...)
- Add loyalty rewards card to storefront account dashboard
- Fix merchant overview to resolve merchant via get_merchant_for_current_user_page
- Fix store login to use store's primary platform for JWT token (interim fix)
- Fix apiClient to attach status/errorCode to thrown errors (fixes error.status
  checks in 12+ JS files — loyalty settings, terminal, email templates, etc.)
- Hide "Add Product" sidebar button when catalog module is not enabled
- Add proposal doc for proper platform detection in store login flow

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

app/modules/customers/templates/customers/storefront/dashboard.html

@@ -66,6 +66,35 @@
             </div>
         </a>
 
+        {% if 'loyalty' in enabled_modules %}
+        <!-- Loyalty Rewards Card -->
+        <a href="{{ base_url }}account/loyalty"
+           class="block bg-white dark:bg-gray-800 rounded-lg shadow hover:shadow-lg transition-shadow p-6 border border-gray-200 dark:border-gray-700"
+           x-data="{ points: null, loaded: false }"
+           x-init="fetch('/api/v1/storefront/loyalty/card').then(r => r.json()).then(d => { if (d.card) { points = d.card.points_balance; } loaded = true; }).catch(() => { loaded = true; })">
+            <div class="flex items-center mb-4">
+                <div class="flex-shrink-0">
+                    <span class="h-8 w-8 text-primary" style="color: var(--color-primary)" x-html="$icon('gift', 'h-8 w-8')"></span>
+                </div>
+                <div class="ml-4">
+                    <h3 class="text-lg font-semibold text-gray-900 dark:text-white">Loyalty Rewards</h3>
+                    <p class="text-sm text-gray-600 dark:text-gray-400">View your points & rewards</p>
+                </div>
+            </div>
+            <div>
+                <template x-if="loaded && points !== null">
+                    <div>
+                        <p class="text-2xl font-bold text-primary" style="color: var(--color-primary)" x-text="points.toLocaleString()"></p>
+                        <p class="text-sm text-gray-500 dark:text-gray-400">Points Balance</p>
+                    </div>
+                </template>
+                <template x-if="loaded && points === null">
+                    <p class="text-sm text-gray-500 dark:text-gray-400">Join our rewards program</p>
+                </template>
+            </div>
+        </a>
+        {% endif %}
+
         <!-- Messages Card -->
         <a href="{{ base_url }}account/messages"
            class="block bg-white dark:bg-gray-800 rounded-lg shadow hover:shadow-lg transition-shadow p-6 border border-gray-200 dark:border-gray-700"