Free days, vacation forfeiture, and global auto-replanning

Free days (Sat/Sun/red days, subject to DayOverride) can never be
vacation, and can only be parental leave when the workspace opts in via
take_pl_on_red_days. The allocator already honoured this; the hand-pin
path bypassed it entirely.

- PlanningService gains optional workspace_repo/day_override_repo deps
  and _reject_illegal_free_day, enforced in add_planned_day and update.
  Reuses allocation_service.is_free_day rather than re-deriving it, and
  no-ops when the deps are unset so existing callers are unaffected.
- update_planned_day had no ValidationError handler at all, so a
  validation failure there 500'd instead of 422'ing. Fixed.
- Calendar filters the pin write loop by the day's isFree; the modal
  explains free days stay off, and that pinning opts a day out of
  automatic re-planning.

Vacation days at risk of forfeiture were computed and sent over the
wire but never rendered: an at-risk column with the age-out/over-cap
split, and a dashboard key figure.

PlanProposal.warnings was likewise parsed but rendered nowhere, for all
three kinds. Adds PlanWarningCard in a Risks section above the tips,
with parent names resolved and dates formatted.

POST /api/plan/sync now fires from the workspace layer on every
plan-input change rather than only from Calendar, so a Settings edit or
a pinned-day save re-plans day types instead of merely refetching.
Overlapping bumps coalesce into one trailing run; a rejection cannot
wedge the in-flight guard. eviction_preview was silently dropped by the
frontend despite always being on the wire, and is now surfaced through
context.

Verified: backend 890 passed (91.49% coverage), frontend 1297 passed,
ruff/eslint/tsc clean. Browser-checked in Swedish and English.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JVQx4NUvPbJhn6UcvRd2QY

frontend/src/i18n/sv/calendar.ts

@@ -4,6 +4,8 @@ export const calendar = {
   'calendar.deleteError': 'Det gick inte att ta bort den planerade dagen',
   'calendar.nextMonthAria': 'Nästa månad',
   'calendar.partner': 'Partner',
+  'calendar.pinnedDayAllFreeError':
+    'Ingen av de valda dagarna kan sparas som den typen — lediga dagar (helg/röd dag) kan aldrig bli semester, och föräldrapenning på dem kräver att inställningen i Inställningar är påslagen.',
   'calendar.prevMonthAria': 'Föregående månad',
   'calendar.saveError': 'Det gick inte att spara de planerade dagarna',
   'calendar.today': 'Idag',
@@ -37,6 +39,10 @@ export const calendar = {
   'plannedDayModal.newTitle': 'Planera en dag',
   'plannedDayModal.parentLabel': 'Förälder',
   'plannedDayModal.pinnedNotice': 'Den här dagen är låst av dig — planeraren ändrar den inte automatiskt.',
+  'plannedDayModal.pinExcludesFromSyncNotice':
+    'Att låsa en dag utesluter den från planerarens automatiska omplanering.',
+  'plannedDayModal.freeDaysStayOffNotice':
+    'Lediga dagar (helg/röd dag) i urvalet lämnas lediga — semester går aldrig att lägga dit, och föräldrapenning kräver att "Ta ut föräldrapenning på röda dagar" är påslaget i Inställningar.',
   'plannedDayModal.excludedNotice': 'Du har tagit bort den här dagen för {parent}.',
   'plannedDayModal.restoreExcludedButton': 'Lägg tillbaka dagen',
   'plannedDayModal.rangeTitle': 'Planera {count} dagar',