fix(storefront-i18n): dashboard widgets translate + correct customer-module key paths

Two bugs from Test 5.1 on FR storefront dashboard:

1. Loyalty + Orders dashboard cards (`StorefrontDashboardCard.title`/
   `subtitle`/`value_label`) were hardcoded English. Added `language`
   to `WidgetContext`; customer dashboard route passes
   `request.state.language` through; loyalty and orders widget
   providers now call `translate(..., context.language)` with new
   `widget.*` i18n keys × 4 locales each.

2. Customer-module locale JSON has redundant top-level `customers`
   wrapper, so after the module-locale loader auto-namespaces under
   module code `customers`, the actual key path is
   `customers.customers.customer_number` (matches the existing
   `loyalty.loyalty.wallet.apple` pattern). My earlier sweep used the
   single-prefix path for 8 references — fixed all to double-prefix.

Both bugs were visible end-of-day yesterday after the api container
recreate landed `1bade6e6`.

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

app/modules/contracts/widgets.py

@@ -72,12 +72,14 @@ class WidgetContext:
         date_to: End of date range filter
         limit: Maximum number of items for list widgets
         include_details: Whether to include extra details (may be expensive)
+        language: Storefront/dashboard locale (e.g. "fr") for i18n of card strings
     """
 
     date_from: datetime | None = None
     date_to: datetime | None = None
     limit: int = 5
     include_details: bool = False
+    language: str | None = None
 
 
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