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.

backend/app/db/connection.py

@@ -19,8 +19,6 @@ _FULL_SCHEMA = """
 CREATE TABLE IF NOT EXISTS workspace (
     id TEXT PRIMARY KEY,
     name TEXT NOT NULL,
-    planning_goal TEXT NOT NULL DEFAULT 'balanced'
-        CHECK (planning_goal IN ('max_time','max_money','balanced')),
     planning_mode TEXT NOT NULL DEFAULT 'solo'
         CHECK (planning_mode IN ('solo','couple')),
     created_at TIMESTAMP NOT NULL
@@ -91,6 +89,7 @@ CREATE TABLE IF NOT EXISTS leave_wish (
     window_end_day INTEGER NOT NULL DEFAULT 1
         CHECK (window_end_day >= 1 AND window_end_day <= 31),
     target_weeks INTEGER NOT NULL,
+    target_days INTEGER,
     recurrence TEXT NOT NULL DEFAULT 'once'
         CHECK (recurrence IN ('yearly','once')),
     first_year INTEGER NOT NULL DEFAULT 2026,
@@ -99,8 +98,6 @@ CREATE TABLE IF NOT EXISTS leave_wish (
     parent_mode TEXT NOT NULL DEFAULT 'either'
         CHECK (parent_mode IN ('either','both','specific')),
     parent_personal_data_uuid TEXT,
-    goal_override TEXT
-        CHECK (goal_override IS NULL OR goal_override IN ('max_time','max_money','balanced')),
     window_mode TEXT NOT NULL DEFAULT 'fixed'
         CHECK (window_mode IN ('fixed','flexible')),
     created_at TIMESTAMP NOT NULL,
@@ -154,12 +151,15 @@ CREATE TABLE IF NOT EXISTS planned_leave_day (
     date DATE NOT NULL,
     day_type TEXT NOT NULL CHECK (day_type IN ('sjukpenning','lagsta','vacation')),
     is_dubbeldag INTEGER NOT NULL DEFAULT 0,
+    wish_id TEXT,
+    is_pinned INTEGER NOT NULL DEFAULT 0,
     created_at TIMESTAMP NOT NULL,
     updated_at TIMESTAMP NOT NULL,
     UNIQUE(workspace_id, child_id, date, parent_personal_data_uuid),
     FOREIGN KEY (workspace_id) REFERENCES workspace(id) ON DELETE CASCADE,
     FOREIGN KEY (child_id) REFERENCES child(id) ON DELETE CASCADE,
-    FOREIGN KEY (parent_personal_data_uuid) REFERENCES personal_data(uuid) ON DELETE CASCADE
+    FOREIGN KEY (parent_personal_data_uuid) REFERENCES personal_data(uuid) ON DELETE CASCADE,
+    FOREIGN KEY (wish_id) REFERENCES leave_wish(id) ON DELETE SET NULL
 );
 
 CREATE TABLE IF NOT EXISTS day_override (