Gift-card rolling expiry, SvelteDate→Date purge, strict DST tests, UTC scan-location + settings legal floor

Gift-card rolling expiry (setting-driven, was dead config):
- GetGiftCardExpiryMonths(): single source of truth (business_settings
  gift_card_expiry_months, fallback 24) shared by payment handlers and the
  CleanupExpiredGiftCards job (was hardcoded 24).
- expiry_date now maintained on ALL 9 gift-card write sites (buy, topup,
  transfer, redeem, terminal payment, refund credit, till) so the refund-time
  guard at refunds.go actually fires. Schema default 12->24 + migration note;
  test-DB seed aligned. Stale "expiry_date IS NULL" test rewritten; new
  expired-card-rejected regression test.

Frontend SvelteDate purge (docs' stated convention, wide):
- All 180+ raw `new SvelteDate(...)` uses across routes/components replaced
  with parseWallClockDate (backend UTC ISO) or new Date (wall-clock
  constructors). SvelteDate imports removed. timeSlots.ts getDayWithOrdinal
  fixed. Zero SvelteDate references remain; svelte-check clean.

Strict timezone/DST testing + QA fixes:
- 8 new hermetic boundary tests: clock.DST transitions (both 2026 folds),
  closing-hours GMT vs BST, booking date-window midnight, refund-tier
  elapsed-time independence, deposit-window UTC-instant, scheduling
  LondonDateString midnight, today AT TIME ZONE window + UTC round-trip.
- today.go summary date labels fixed to London wall-clock (were showing the
  previous UTC day during BST) + regression test.
- pgx ScanLocation fixed to UTC via AfterConnect (was host-local -> JSON
  offsets depended on deployment TZ, contradicting the documented UTC
  invariant) + regression test. Registered as a new *Type to avoid a data
  race on the shared type map (caught by -race).

Admin Business Settings (setting now functional => legal floor):
- gift_card_expiry_months validation floor raised 1 -> 12 months (CMA/
  Consumer Rights Act 2015 unfair-contract-term guidance) in endpoint + UI,
  with rolling-expiry semantics shown in both display and edit form.
- 3 new expiry validation tests; 2 pre-existing message assertions updated.

Full suite 25/25 + race clean via run-tests.sh lockfile; svelte-check 0
errors/warnings; production build succeeds.

backend/handlers/today/today.go

@@ -228,11 +228,15 @@ func GetCurrentAndNextHandler(w http.ResponseWriter, r *http.Request) {
 		response.DoneForDay = &done
 
 		if todayOpen {
-			// Regular done-for-the-day: show daily summary
+			// Regular done-for-the-day: show daily summary. Format the dates in
+			// Europe/London: todayStart is London midnight converted to UTC (e.g.
+			// 2026-08-04 00:00 BST = 2026-08-03 23:00 UTC), so formatting the UTC
+			// instant directly yields the PREVIOUS day during BST. Use the
+			// London-located instant so the summary header shows the business day.
 			summary := computeAggregateSummary(r, todayStart, todayEnd)
 			summary.SummaryScope = "day"
-			summary.SummaryStartDate = todayStart.Format("2006-01-02")
-			summary.SummaryEndDate = todayEnd.Format("2006-01-02")
+			summary.SummaryStartDate = todayStart.In(londonLocation).Format("2006-01-02")
+			summary.SummaryEndDate = todayEnd.In(londonLocation).Format("2006-01-02")
 			response.Summary = summary
 
 			// If tomorrow is closed, also compute a week summary
@@ -241,8 +245,8 @@ func GetCurrentAndNextHandler(w http.ResponseWriter, r *http.Request) {
 				weekStart, _ := findWeekSummaryRange(r, tomorrow)
 				ws := computeAggregateSummary(r, weekStart, todayEnd)
 				ws.SummaryScope = "week"
-				ws.SummaryStartDate = weekStart.Format("2006-01-02")
-				ws.SummaryEndDate = todayStart.Format("2006-01-02")
+				ws.SummaryStartDate = weekStart.In(londonLocation).Format("2006-01-02")
+				ws.SummaryEndDate = todayStart.In(londonLocation).Format("2006-01-02")
 				response.WeekSummary = ws
 			}
 		} else {
@@ -250,8 +254,8 @@ func GetCurrentAndNextHandler(w http.ResponseWriter, r *http.Request) {
 			weekStart, _ := findWeekSummaryRange(r, londonNow)
 			summary := computeAggregateSummary(r, weekStart, todayEnd)
 			summary.SummaryScope = "week"
-			summary.SummaryStartDate = weekStart.Format("2006-01-02")
-			summary.SummaryEndDate = todayStart.Format("2006-01-02")
+			summary.SummaryStartDate = weekStart.In(londonLocation).Format("2006-01-02")
+			summary.SummaryEndDate = todayStart.In(londonLocation).Format("2006-01-02")
 			response.Summary = summary
 		}
 	}