Seed household settings at boot and serve the settings API

Port of Feature 04 task 3 (7629cab) onto Feature 04 + Feature 03.

On first boot create the single household_settings row with the zone from
MEALQUEST_DEFAULT_TZ and the seed times and days (dinner 17:30, reminder
16:30, rotation check 09:00, plan draft Fri 09:00, suggestions Sun 08:00,
chat autosend Sat 08:00). An existing row is never overwritten.

Add household.SettingsService with Get, a validating Update (IANA zone,
zero-padded 24-hour HH:MM, day of week 0-6) that records updated_by, and
in-process Subscribe for the scheduler. Serve it as GET and PATCH
/api/v1/settings/household; invalid input is a 400 in the standard error
body. Migration 0002 adds household_settings.updated_by. Link time/tzdata
from internal/household so zones load in the minimal image.

Review fixes:
- F1: the settings routes are mounted on the protected /api/v1 subrouter,
  so they need a session (RequireSession) and, for PATCH, the CSRF token.
  updated_by is the session actor's subject from auth.ActorFrom; the
  duplicate internal/actor package is dropped, and Update refuses an empty
  member instead of storing NULL. A test drives PATCH through the
  production router with a real SessionManager session.
- F2: config no longer validates MEALQUEST_DEFAULT_TZ. Seeding requires a
  valid zone only when it creates the row (ErrNoDefaultZone,
  ErrInvalidDefaultZone, both naming the variable at boot), so a reboot
  over existing settings ignores a missing or invalid default.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/store/migrate_test.go

@@ -175,8 +175,8 @@ func TestMigrateEmbeddedMigrations(t *testing.T) {
 	if err := Migrate(context.Background(), s.Writer, migrations.FS); err != nil {
 		t.Fatal(err)
 	}
-	if got := versions(migrationRows(t, s)); got != "0000_bootstrap,0001_init" {
-		t.Errorf("versions = %q, want 0000_bootstrap,0001_init", got)
+	if got := versions(migrationRows(t, s)); got != "0000_bootstrap,0001_init,0002_household_settings_updated_by" {
+		t.Errorf("versions = %q, want 0000_bootstrap,0001_init,0002_household_settings_updated_by", got)
 	}
 }
 
@@ -188,15 +188,16 @@ func TestMigrateBootstrapThenEmbeddedInitApplies(t *testing.T) {
 		t.Fatal(err)
 	}
 	// A database migrated by the bootstrap-only build upgrades to the
-	// embedded set, which adds 0001_init.sql alongside the unchanged bootstrap.
+	// embedded set, which adds the later migrations alongside the unchanged
+	// bootstrap.
 	if err := Migrate(ctx, s.Writer, fstest.MapFS{"0000_bootstrap.sql": {Data: bootstrap}}); err != nil {
 		t.Fatal(err)
 	}
 	if err := Migrate(ctx, s.Writer, migrations.FS); err != nil {
 		t.Fatal(err)
 	}
-	if got := versions(migrationRows(t, s)); got != "0000_bootstrap,0001_init" {
-		t.Errorf("versions = %q, want 0000_bootstrap,0001_init", got)
+	if got := versions(migrationRows(t, s)); got != "0000_bootstrap,0001_init,0002_household_settings_updated_by" {
+		t.Errorf("versions = %q, want 0000_bootstrap,0001_init,0002_household_settings_updated_by", got)
 	}
 	if !tableExists(t, s, "dinners") {
 		t.Error("table from 0001_init was not created")