Link planned days to their wish, fix the age-4 cap, drop the planning goal

Three changes that together unblock treating a calendar period as one
editable object.

Migration 008 adds `planned_leave_day.wish_id` (nullable, ON DELETE SET NULL)
so a persisted day knows which `leave_wish` produced it, `is_pinned` to mark a
day the user hand-edited, and `leave_wish.target_days` so a period drawn on a
calendar need not be a whole number of weeks. Apply-time identity still keys on
day_type/is_dubbeldag only, so a wish_id-only difference is a metadata update
rather than a collision.

The age-4 savable ceiling was applying the per-child figure of 96 to each
parent's pool, modelling a two-parent family as able to save 192 days past the
child's fourth birthday. `resolve_age4_savable_cap` is now the single place
that decides 48 (couple with two parents) versus 96 (everyone else), and both
AnalyticsService and the allocator read it.

Migration 009 drops `workspace.planning_goal` and `leave_wish.goal_override`.
The allocator's tier-3 policy collapses to one rule; `salary_type` still
branches, since that reflects what a vacation day actually costs a parent
rather than a user preference.

frontend/src/pages/Settings.tsx

@@ -15,7 +15,6 @@ import { Layout } from '@/components/layout/Layout'
 import { LoadingSpinner } from '@/components/common/LoadingSpinner'
 import { ChildBirthdayInput } from '@/components/inputs/ChildBirthdayInput'
 import { ParentProfileInput, type SalaryType, type EmploymentStatus } from '@/components/inputs/ParentProfileInput'
-import { PlanningGoalSelector, type PlanningGoal } from '@/components/inputs/PlanningGoalSelector'
 import { PlanningModeSelector, type PlanningMode } from '@/components/inputs/PlanningModeSelector'
 import { VacationDaysInput } from '@/components/inputs/VacationDaysInput'
 import { VacationDaysTable, type VacationDaysTableRow } from '@/components/vacation-days/VacationDaysTable'
@@ -132,7 +131,6 @@ export function Settings(): ReactNode {
   const [childBirthDate, setChildBirthDate] = useState('')
   const [preschoolPlanningDays, setPreschoolPlanningDays] = useState(6)
   const [parentData, setParentData] = useState<{ salaryType?: SalaryType; employmentStatus?: EmploymentStatus }>({})
-  const [planningGoal, setPlanningGoal] = useState<PlanningGoal>(workspace?.planningGoal ?? 'balanced')
   const [planningMode, setPlanningMode] = useState<PlanningMode>(workspace?.planningMode ?? 'solo')
   const [saveMessage, setSaveMessage] = useState<{ type: 'success' | 'error'; text: string } | null>(null)
   const [isSaving, setIsSaving] = useState(false)
@@ -152,13 +150,10 @@ export function Settings(): ReactNode {
   }, [childDetails])
 
   useEffect(() => {
-    if (workspace?.planningGoal) {
-      setPlanningGoal(workspace.planningGoal)
-    }
     if (workspace?.planningMode) {
       setPlanningMode(workspace.planningMode)
     }
-  }, [workspace?.planningGoal, workspace?.planningMode])
+  }, [workspace?.planningMode])
 
   const selectedChild = children.find((c) => c.id === selectedChildId)
   const hasPartner = members.some((m) => m.uuid !== personalDataUuid)
@@ -256,7 +251,7 @@ export function Settings(): ReactNode {
     try {
       if (workspace?.id) {
         setIsSaving(true)
-        await api.updateWorkspace(workspace.id, { planningGoal, planningMode })
+        await api.updateWorkspace(workspace.id, { planningMode })
         await refreshContext()
         showMessage('success', t('settings.savePlanningSuccess'))
       }
@@ -442,7 +437,6 @@ export function Settings(): ReactNode {
         <section className="settings-page__section">
           <h2>{t('settings.planningSectionTitle')}</h2>
           <p className="settings-page__help">{t('settings.planningHelp')}</p>
-          <PlanningGoalSelector value={planningGoal} onChange={setPlanningGoal} />
           <PlanningModeSelector value={planningMode} onChange={setPlanningMode} />
           <button
             onClick={handleSavePlanning}