refactor: plan timeframes use a per-day-of-week picker (like the V2 tariff)

The timeframes model was a coarse weekday/weekend split, which couldn't express
"open Saturdays" or different rules on a specific day — and it didn't match the
V2 tariff, which already has a proper per-day-of-week picker (Hën–Die).

Replace PlanTimeframes { weekday, weekend } with { days[], fromMin, toMin }: the
allowed window applies only on the selected days (0=Sun..6=Sat; empty = every
day); on unselected days the subscriber parks free. A "night plan, free
weekends" is just days [Mon..Fri] with a 20:00→08:00 window — the exact case
from before, now expressible alongside any other day combination.

outOfWindowGap reworked to the days model (per-day membership test instead of
the weekend helper); the plans editor reuses the tariff composer's Mon-first
checkbox row and the shared tariff.dow0..6 labels. No production plans carry
timeframes yet (feature shipped today), so the shape changed directly with no
migration. Unit tests updated + extended (Saturday-only, every-day, weekday
night); 81 shared tests pass. Build+lint 12/12.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/lib/i18n/en.ts

@@ -469,12 +469,12 @@ export const en: Catalog = {
     saved: "Plan saved.",
     confirmRetire: "Retire the plan “{{name}}”? It will no longer be sellable (history is kept).",
     needWindow: "Enter valid window times (HH:MM).",
+    needDays: "Select at least one day for the window.",
     restrictTimes: "Restrict parking times (charge transient tariff outside the window)",
-    weekdayWindow: "Weekday",
+    days: "Days",
+    window: "Window",
     enterAfter: "enter after",
     exitBefore: "· exit before",
-    weekend: "Weekend",
-    weekendAllDay: "all day (no restriction)",
     grace: "Grace",
     graceHint: "minutes tolerance around the window edges",
     timeframesHint: "A scan outside the allowed window is charged the normal transient tariff for the out-of-window minutes (early entry is deferred to exit; late exit is gated until paid).",