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/api.ts

@@ -494,16 +494,13 @@ export interface SubscriptionCredential {
 }
 export type SubscriptionPeriod = "day" | "week" | "month";
 
-/** A subscriber's allowed parking window for a day-type (minutes-from-local-midnight).
- *  A scan outside the window is charged the transient tariff for the gap. */
-export interface DayWindow {
-  allDay?: boolean;
-  fromMin?: number;
-  toMin?: number;
-}
+/** A subscriber's allowed parking window (minutes-from-local-midnight) on selected days.
+ *  A scan outside the window is charged the transient tariff for the gap. days: 0=Sun..6=Sat
+ *  (empty = every day); the window [fromMin,toMin) wraps past midnight when toMin ≤ fromMin. */
 export interface PlanTimeframes {
-  weekday?: DayWindow;
-  weekend?: DayWindow;
+  days?: number[];
+  fromMin: number;
+  toMin: number;
   graceMin?: number;
   tz?: string;
 }