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/en/calendar.ts

@@ -4,6 +4,8 @@ export const calendar = {
   'calendar.deleteError': 'Failed to delete the planned day',
   'calendar.nextMonthAria': 'Next month',
   'calendar.partner': 'Partner',
+  'calendar.pinnedDayAllFreeError':
+    'None of the selected days can be saved as that type — free days (weekends/red days) can never be vacation, and parental leave on them needs the Settings toggle turned on.',
   'calendar.prevMonthAria': 'Previous month',
   'calendar.saveError': 'Failed to save the planned days',
   'calendar.today': 'Today',
@@ -37,6 +39,10 @@ export const calendar = {
   'plannedDayModal.newTitle': 'Plan a Day',
   'plannedDayModal.parentLabel': 'Parent',
   'plannedDayModal.pinnedNotice': 'This day is pinned by you — the planner will not change it automatically.',
+  'plannedDayModal.pinExcludesFromSyncNotice':
+    'Pinning excludes this day from the planner’s automatic re-planning.',
+  'plannedDayModal.freeDaysStayOffNotice':
+    'Free days (weekends/red days) in your selection are left as days off — vacation can never go there, and parental leave needs "Take parental leave on red days" turned on in Settings.',
   'plannedDayModal.excludedNotice': 'You removed this day for {parent}.',
   'plannedDayModal.restoreExcludedButton': 'Put the day back',
   'plannedDayModal.rangeTitle': 'Plan {count} days',