fix(storefront-auth): apiClient redirects to login on 401 from /account/*

When the customer's JWT (30-min TTL via JWT_EXPIRE_MINUTES) expires in
localStorage, subsequent API calls from a customer-area page returned
401 → callers showed an unrelated error UI (loyalty dashboard rendered
the "join now" CTA because card came back null on the catch path).

Three changes in static/shared/js/api-client.js:

1. Path detection in getToken() + clearTokens() now recognises
   /account/* and /api/v1/storefront/* as customer-area routes (the
   only existing checks were for /shop/* which was never used in this
   codebase). Also clears customer_user alongside customer_token.

2. New redirectIfCustomerAreaUnauthorized() helper: on a /account/*
   page, sends the browser to /account/login?next=<current path>
   (with a guard to skip the redirect when already on the login page,
   avoiding loops). Called from all three 401 paths (request,
   requestFormData, getBlob).

3. login.html now honours the ?next= query param (in addition to the
   legacy ?return=), so the redirect lands the user back where their
   session expired.

Other personas (admin/store/merchant) are unaffected — the helper is
a no-op outside /account/*.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

static/shared/js/api-client.js

@@ -56,7 +56,12 @@ class APIClient {
         } else if (currentPath.startsWith('/admin/') || currentPath.startsWith('/api/v1/admin/')) {
             token = adminToken;
             source = 'admin (path-based)';
-        } else if (currentPath.includes('/shop/') || currentPath.startsWith('/api/v1/shop/')) {
+        } else if (
+            currentPath.startsWith('/account/') ||
+            currentPath.startsWith('/api/v1/storefront/') ||
+            currentPath.includes('/shop/') ||
+            currentPath.startsWith('/api/v1/shop/')
+        ) {
             token = customerToken;
             source = 'customer (path-based)';
         } else if (currentPath.startsWith('/merchants/') || currentPath.startsWith('/api/v1/merchants/')) {
@@ -145,12 +150,13 @@ class APIClient {
                 }
             }
 
-            // Handle 401 Unauthorized - Just clear tokens, DON'T redirect
+            // Handle 401 Unauthorized
             if (response.status === 401) {
                 apiLog.warn('401 Unauthorized - Authentication failed');
                 apiLog.debug('Error details:', data);
                 apiLog.info('Clearing authentication tokens');
                 this.clearTokens();
+                this.redirectIfCustomerAreaUnauthorized();
 
                 const errorMessage = data.message || data.detail || 'Unauthorized - please login again';
                 apiLog.error('Throwing authentication error:', errorMessage);
@@ -299,6 +305,7 @@ class APIClient {
             if (response.status === 401) {
                 apiLog.warn('401 Unauthorized - Authentication failed');
                 this.clearTokens();
+                this.redirectIfCustomerAreaUnauthorized();
                 throw new Error(data.message || data.detail || 'Unauthorized');
             }
 
@@ -339,6 +346,7 @@ class APIClient {
             if (response.status === 401) {
                 apiLog.warn('401 Unauthorized - Authentication failed');
                 this.clearTokens();
+                this.redirectIfCustomerAreaUnauthorized();
                 throw new Error('Unauthorized');
             }
 
@@ -395,9 +403,15 @@ class APIClient {
             localStorage.removeItem('store_user');
             localStorage.removeItem('currentUser');
             localStorage.removeItem('storeCode');
-        } else if (currentPath.includes('/shop/') || currentPath.startsWith('/api/v1/shop/')) {
+        } else if (
+            currentPath.startsWith('/account/') ||
+            currentPath.startsWith('/api/v1/storefront/') ||
+            currentPath.includes('/shop/') ||
+            currentPath.startsWith('/api/v1/shop/')
+        ) {
             apiLog.info('Clearing customer tokens only');
             localStorage.removeItem('customer_token');
+            localStorage.removeItem('customer_user');
         } else if (currentPath.startsWith('/merchants/') || currentPath.startsWith('/api/v1/merchants/')) {
             apiLog.info('Clearing merchant tokens only');
             localStorage.removeItem('merchant_token');
@@ -426,6 +440,28 @@ class APIClient {
         apiLog.info('Context-specific tokens cleared');
     }
 
+    /**
+     * If the user is on a customer-area page (/account/*) and gets 401,
+     * send them to the login page with a return URL so they land back
+     * here after re-authenticating.
+     *
+     * No-op for admin/store/merchant areas — those callers handle 401
+     * their own way. Also no-op if already on the login page (avoids
+     * a redirect loop).
+     *
+     * Returns true if a redirect was scheduled (caller should suppress
+     * its own error UI since the page is about to navigate away).
+     */
+    redirectIfCustomerAreaUnauthorized() {
+        const path = window.location.pathname;
+        const onCustomerArea = path.startsWith('/account/') && path !== '/account/login';
+        if (!onCustomerArea) return false;
+        const next = encodeURIComponent(path + window.location.search);
+        apiLog.info('Redirecting to /account/login (session expired), next=' + next);
+        window.location.href = `/account/login?next=${next}`;
+        return true;
+    }
+
     /**
      * Handle unauthorized access
      * DEPRECATED - Now just clears tokens, doesn't redirect