fix(storefront): i18n sweep + locale-aware reset-password and welcome email

Test 5 (storefront password reset + customer dashboard) surfaced five
issues that all traced back to missing i18n plumbing:

- Forgot-password email arrived in EN regardless of storefront locale —
  handler now prefers request.state.language over customer.preferred_language,
  and loyalty self-enrollment backfills preferred_language for new + returning
  customers so future locale-sensitive flows hit the right language without
  being told twice.
- reset-password.html rendered "undefined" icon boxes because $icon magic
  wasn't loaded in the standalone page — replaced with inline SVGs matching
  the forgot-password.html convention.
- reset-password.html was hardcoded English: added lang attr, full _()
  sweep (22 new auth.* keys × 4 locales), language selector, and JS
  validation strings exposed via tojson.
- "Continue shopping" CTA renamed to "Back to Home" (auth.back_to_home,
  4 locales) on login + forgot + reset — loyalty storefronts have no
  catalog to continue to, mirroring the earlier enroll-success rename.
- /account dashboard, profile, addresses were hardcoded English in the
  body (menu was FR because base layout uses _()). New customers.storefront
  .pages.{dashboard,profile,addresses}.* namespace (~80 keys × 4 locales),
  templates updated, Alpine JS strings injected via window.__*I18n.

18 files, 18 changed; arch validation: 126 warnings before = 126 after,
mkdocs --strict clean.

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

app/modules/loyalty/routes/api/storefront.py

@@ -94,6 +94,7 @@ def self_enroll(
         customer_name=data.customer_name,
         customer_phone=data.customer_phone,
         customer_birthday=data.customer_birthday,
+        customer_language=getattr(request.state, "language", None),
     )
 
     logger.info(f"Self-enrollment for customer {customer_id} at store {store.subdomain}")

app/modules/loyalty/services/card_service.py

@@ -188,6 +188,7 @@ class CardService:
         customer_name: str | None = None,
         customer_phone: str | None = None,
         customer_birthday: date | None = None,
+        customer_language: str | None = None,
     ) -> int:
         """
         Resolve a customer ID from either a direct ID or email lookup.
@@ -224,11 +225,18 @@ class CardService:
 
             customer = customer_service.get_customer_by_email(db, store_id, email)
             if customer:
-                # Backfill birthday on existing customer if they didn't have
-                # one before — keeps the enrollment form useful for returning
-                # customers who never previously provided a birthday.
+                # Backfill birthday + preferred_language on existing customer
+                # if they were missing — keeps the enrollment form useful for
+                # returning customers and lets transactional emails (welcome,
+                # password reset) hit the right locale.
+                dirty = False
                 if customer_birthday and not customer.birth_date:
                     customer.birth_date = customer_birthday
+                    dirty = True
+                if customer_language and not customer.preferred_language:
+                    customer.preferred_language = customer_language
+                    dirty = True
+                if dirty:
                     db.flush()
                 return customer.id
 
@@ -250,8 +258,17 @@ class CardService:
                     .first()
                 )
                 if existing_cardholder:
+                    dirty = False
                     if customer_birthday and not existing_cardholder.birth_date:
                         existing_cardholder.birth_date = customer_birthday
+                        dirty = True
+                    if (
+                        customer_language
+                        and not existing_cardholder.preferred_language
+                    ):
+                        existing_cardholder.preferred_language = customer_language
+                        dirty = True
+                    if dirty:
                         db.flush()
                     return existing_cardholder.id
 
@@ -272,6 +289,7 @@ class CardService:
                     last_name=last_name,
                     phone=customer_phone,
                     birth_date=customer_birthday,
+                    preferred_language=customer_language,
                 )
                 logger.info(
                     f"Created customer {customer.id} ({email}) "