Fix tip amount-change false dedup, wire BuyerEmail everywhere, clear ESLint errors

Money-moving fixes:
- Tip idempotency key regenerates when the tip amount changes after a failed
  attempt (all 3 tip flows). Cached key still reused on same-amount retry
  (dedup intact) and cleared on success/modal reset. Prevents silent
  under-charge when a user retries at a different amount.
- Till replay path returns actual till_sales.status (may be 'pending') instead
  of hardcoded 'completed' — no more misreported successful charge.
- BuyerEmail wired for CreateBookingPayment, gift card purchases, and till
  sales (saved_card + online_square), matching the tip flow. Email lookup
  errors logged, non-fatal.
- Till buyer-email errors now logged (was silently swallowed).
- on_the_house till top-up uses cached getIdempotencyKey() for retry-safe dedup
  (was fresh crypto.randomUUID()).

Test/validation fixes:
- Add TestPaymentFromSquare_* unit tests (else-branch + nil card details),
  build tag relaxed to 'test' so they run in the standard dev suite.
- Add TestValidateCardInfo table test (7 cases: both/either/neither/empty).
- Add TestCreateTillSale_TwoIdenticalCreateSales_BothSucceed regression test.
- Remove dead mock pre-registration in TestTipPayment_WithSavedCard.
- Correct misleading till regression-test comment.

ESLint cleanup (12 errors -> 0):
- Remove unused loadingCards in tip + pay-tip pages (dead assignments in
  loadSavedCards).
- Scoped eslint-disable for {@html} in CardBrandIcon (hardcoded brand SVGs).
- Remove dead confirmSaveDefaultHours + unused rescheduleVersion prop in
  WeeklySchedule (and its parent pass-through).
- Replace new Date() with SvelteDate in WeeklySchedule + BusinessHours.
- Fix each-block key in BusinessHours skeleton loader.
- Use void expression for reactivity-tracker reads in effects.

frontend/src/lib/components/admin/GiftCardsManagement.svelte

@@ -694,7 +694,7 @@
 				amount: Number(topUpAmount),
 				payment_method: 'on_the_house',
 				gift_card_id: gcId,
-				idempotency_key: 'till-on-the-house-' + gcId + '-' + Date.now()
+				idempotency_key: getIdempotencyKey()
 			};
 
 			const res = await apiFetch('/api/admin/till/sale', {