Author leave on the calendar itself

Planning used to mean filling in a wish list on one tab, pressing a button to
see a suggestion, then pressing another to accept it — with nothing on screen
telling you whether a plan was active. Dragging a range on the calendar now
creates the period directly, clicking a band opens it for editing, and each
change is recomputed and saved in one step. A period repeats never or yearly,
matching what the planner can actually express.

Clicking a day edits that day: its funding type, which pins it so the planner
leaves it alone, and whether the day counts as worked or off. That switch used
to be a mode covering the whole grid, which is what made the calendar confusing.

The season presets move to a rail beside the grid. Picking one lets the planner
choose the placement, then jumps there and flashes it, rather than asking the
user to guess dates the engine already knows.

A sync that funds nothing now says so, naming the period and how many days it
fell short, instead of leaving the screen unchanged and looking broken.

frontend/src/components/common/CalendarWeek.tsx

@@ -29,8 +29,12 @@ export interface CalendarWeekProps {
   onPointerEnter: (date: string) => void
   /** §3.4/§3.6 — calendar metadata (röda dagar/klämdagar/overrides) keyed by ISO date. */
   calendarDaysByDate?: Map<string, CalendarDayEntry> | undefined
-  /** Optional for now — a later task wires this to a period editor. */
+  /** Opens the period editor for the clicked band's underlying period. */
   onBandClick?: ((info: BandClickInfo) => void) | undefined
+  /** §Task7 — the wishId of a just-created/just-edited period to briefly
+   * highlight (see Calendar.tsx's preset rail: "scrolls to the resolved
+   * placement and flashes the band"). `null`/omitted highlights nothing. */
+  flashWishId?: string | null | undefined
 }
 
 /** One day's slot inside a band segment: either a real planned_leave_day
@@ -241,6 +245,7 @@ export function CalendarWeek({
   onPointerEnter,
   calendarDaysByDate,
   onBandClick,
+  flashWishId,
 }: CalendarWeekProps): ReactNode {
   const { t } = useTranslation()
   const bandSegments = useMemo(
@@ -323,6 +328,7 @@ export function CalendarWeek({
           'calendar-band',
           segment.isBandStart ? 'calendar-band--start' : '',
           segment.isBandEnd ? 'calendar-band--end' : '',
+          segment.wishId && segment.wishId === flashWishId ? 'calendar-band--flash' : '',
         ]
           .filter(Boolean)
           .join(' ')