fix(loyalty): cross-store enrollment, card scoping, i18n flicker

Fix duplicate card creation when the same email enrolls at different
stores under the same merchant, and implement cross-location-aware
enrollment behavior.

- Cross-location enabled (default): one card per customer per merchant.
  Re-enrolling at another store returns the existing card with a
  "works at all our locations" message + store list.
- Cross-location disabled: one card per customer per store. Enrolling
  at a different store creates a separate card for that store.

Changes:
- Migration loyalty_004: replace (merchant_id, customer_id) unique
  index with (enrolled_at_store_id, customer_id). Per-merchant
  uniqueness enforced at application layer when cross-location enabled.
- card_service.resolve_customer_id: cross-store email lookup via
  merchant_id param to find existing cardholders at other stores.
- card_service.enroll_customer: branch duplicate check on
  allow_cross_location_redemption setting.
- card_service.search_card_for_store: cross-store email search when
  cross-location enabled so staff at store2 can find cards from store1.
- card_service.get_card_by_customer_and_store: new service method.
- storefront enrollment: catch LoyaltyCardAlreadyExistsException,
  return existing card with already_enrolled flag, locations, and
  cross-location context. Server-rendered i18n via Jinja2 tojson.
- enroll-success.html: conditional cross-store/single-store messaging,
  server-rendered translations and context, i18n_modules block added.
- dashboard.html, history.html: replace $t() with server-side _() to
  fix i18n flicker across all storefront templates.
- Fix device-mobile icon → phone icon.
- 4 new i18n keys in 4 locales (en, fr, de, lb).
- Docs: updated data-model, business-logic, production-launch-plan,
  user-journeys with cross-location behavior and E2E test checklist.
- 12 new unit tests + 3 new integration tests (334 total pass).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/loyalty/docs/production-launch-plan.md

@@ -40,11 +40,14 @@ This is the active execution plan for taking the Loyalty module to production. I
 ```
 loyalty_002 (existing)
 loyalty_003 — CHECK constraints (points_balance >= 0, stamp_count >= 0, etc.)
-loyalty_004 — seed 28 notification email templates
-loyalty_005 — add columns: last_expiration_warning_at, last_reengagement_at on cards;
+loyalty_004 — relax card uniqueness: replace (merchant_id, customer_id) unique index
+              with (enrolled_at_store_id, customer_id) for cross-location support
+loyalty_005 — seed 28 notification email templates
+loyalty_006 — add columns: last_expiration_warning_at, last_reengagement_at on cards;
               acting_admin_id on transactions
-loyalty_006 — terms_cms_page_slug on programs
-loyalty_007 — birth_date on customers (P0 — Phase 1.4 fix, dropped data bug)
+loyalty_007 — terms_cms_page_slug on programs
+
+customers_003 — birth_date on customers (Phase 1.4 fix, dropped data bug)
 ```
 
 ---
@@ -82,7 +85,7 @@ All 8 decisions locked. No external blockers.
 #### 1.4 Fix dropped birthday data (P0 bug)
 **Background:** The enrollment form (`enroll.html:87`) collects a birthday, the schema accepts `customer_birthday` (`schemas/card.py:34`), and `card_service.resolve_customer_id` has the parameter (`card_service.py:172`) — but the call to `customer_service.create_customer_for_enrollment` at `card_service.py:215-222` does not pass it, and the `Customer` model has no `birth_date` column at all. Every enrollment silently loses the birthday. Not live yet, so no backfill needed.
 
-- New migration `loyalty_007_add_customer_birth_date.py` (or place under customers module if that's the convention) adds `birth_date: Date | None` to `customers`.
+- Migration `customers_003_add_birth_date.py` adds `birth_date: Date | None` to `customers`.
 - Update `customer_service.create_customer_for_enrollment` to accept and persist `birth_date`.
 - Update `card_service.py:215-222` to pass `customer_birthday` through, with `date.fromisoformat()` parsing and validation (must be a real past date, sensible age range).
 - Update `customer_service.update_customer` to allow backfill.
@@ -114,7 +117,7 @@ All 8 decisions locked. No external blockers.
 - New `app/modules/loyalty/tasks/notifications.py` with `@shared_task(name="loyalty.send_notification_email", bind=True, max_retries=3, default_retry_delay=60)`.
 - Opens fresh `SessionLocal`, calls `EmailService(db).send_template(...)`, retries on SMTP errors.
 
-#### 2.3 Seed templates `loyalty_004`
+#### 2.3 Seed templates `loyalty_005`
 - 7 templates × 4 locales (en, fr, de, lb) = **28 rows** in `email_templates`.
 - Template codes: `loyalty_enrollment`, `loyalty_welcome_bonus`, `loyalty_points_expiring`, `loyalty_points_expired`, `loyalty_reward_ready`, `loyalty_birthday`, `loyalty_reengagement`.
 - **Copywriting needs sign-off** before applying to prod.
@@ -123,7 +126,7 @@ All 8 decisions locked. No external blockers.
 - In `card_service.enroll_customer_for_store` (~lines 480-540), call notification service **after** `db.commit()`.
 
 #### 2.5 Wire expiration warning into expiration task
-- Migration `loyalty_005` adds `last_expiration_warning_at` to prevent duplicates.
+- Migration `loyalty_006` adds `last_expiration_warning_at` to prevent duplicates.
 - In rewritten `tasks/point_expiration.py` (see 3.1), find cards 14 days from expiry, fire warning, stamp timestamp.
 - **Validation:** time-mocked test — fires once at 14-day mark.
 
@@ -137,7 +140,7 @@ All 8 decisions locked. No external blockers.
 
 #### 2.8 Re-engagement Celery beat task
 - Weekly schedule. Finds cards inactive > N days (default 60, configurable).
-- Throttled via `last_reengagement_at` (added in `loyalty_005`) — once per quarter per card.
+- Throttled via `last_reengagement_at` (added in `loyalty_006`) — once per quarter per card.
 
 ---
 
@@ -163,7 +166,7 @@ All 8 decisions locked. No external blockers.
 ### Phase 4 — Accessibility & T&C *(2d)*
 
 #### 4.1 T&C via store CMS integration
-- Migration `loyalty_006`: add `terms_cms_page_slug: str | None` to `loyalty_programs`.
+- Migration `loyalty_007`: add `terms_cms_page_slug: str | None` to `loyalty_programs`.
 - Update `schemas/program.py` (`ProgramCreate`, `ProgramUpdate`).
 - `program-form.html:251` — CMS page picker scoped to the program's owning store.
 - `enroll.html:99-160` — resolve slug to CMS page URL/content; legacy `terms_text` fallback.
@@ -224,7 +227,7 @@ All 8 decisions locked. No external blockers.
 - **Admin "act on behalf"** (`routes/api/admin.py`):
   - `POST /admin/loyalty/merchants/{merchant_id}/cards/bulk/deactivate` (etc.)
   - Shared service layer; route stamps `acting_admin_id` in audit log
-- New `loyalty_transactions.acting_admin_id` column in `loyalty_005`.
+- New `loyalty_transactions.acting_admin_id` column in `loyalty_006`.
 
 #### 6.5 Manual override: restore expired points
 - `POST /admin/loyalty/cards/{card_id}/restore_points` with `{points, reason}`.