fix: clean up dangling FK references before deleting a user

Resolves FOREIGN KEY constraint failed (500) on DELETE /api/admin/users/:id
and DELETE /api/auth/me when the target user had rows in trip_members.invited_by,
share_tokens.created_by, budget_items.paid_by_user_id, journeys.user_id,
journey_entries.author_id, journey_contributors.user_id, or
journey_share_tokens.created_by — none of which had ON DELETE clauses.

Introduces deleteUserCompletely() in userCleanupService.ts which wraps all
cleanup and the final DELETE FROM users in a single transaction. Both
adminService.deleteUser and authService.deleteAccount now call it instead of
the bare DELETE. Tests ADMIN-005b and AUTH-040 cover all reference types
including notification sender/recipient and notice dismissals.

server/tests/integration/admin.test.ts

@@ -41,7 +41,7 @@ import { createApp } from '../../src/app';
 import { createTables } from '../../src/db/schema';
 import { runMigrations } from '../../src/db/migrations';
 import { resetTestDb } from '../helpers/test-db';
-import { createUser, createAdmin, createInviteToken } from '../helpers/factories';
+import { createUser, createAdmin, createInviteToken, createTrip, createBudgetItem, createJourney, createJourneyEntry, addJourneyContributor } from '../helpers/factories';
 import { authCookie } from '../helpers/auth';
 import { loginAttempts, mfaAttempts } from '../../src/routes/auth';
 
@@ -148,6 +148,70 @@ describe('Admin user management', () => {
     expect(deleted).toBeUndefined();
   });
 
+  it('ADMIN-005b — DELETE /admin/users/:id succeeds when user has FK references', async () => {
+    const { user: admin } = createAdmin(testDb);
+    const { user: target } = createUser(testDb);
+    const { user: otherUser } = createUser(testDb);
+    const { user: thirdUser } = createUser(testDb);
+
+    // trip_members.invited_by: target invited thirdUser to otherUser's trip
+    // (trip survives deletion; only invited_by should become NULL)
+    const otherTrip = createTrip(testDb, otherUser.id);
+    testDb.prepare('INSERT INTO trip_members (trip_id, user_id, invited_by) VALUES (?, ?, ?)').run(otherTrip.id, thirdUser.id, target.id);
+
+    // share_tokens.created_by: target created a share token for otherUser's trip
+    testDb.prepare("INSERT INTO share_tokens (trip_id, token, created_by) VALUES (?, 'tok-admin-test', ?)").run(otherTrip.id, target.id);
+
+    // budget_items.paid_by_user_id: target paid for an expense on otherUser's trip
+    const budgetItem = createBudgetItem(testDb, otherTrip.id);
+    testDb.prepare('UPDATE budget_items SET paid_by_user_id = ? WHERE id = ?').run(target.id, budgetItem.id);
+
+    // journey_contributors: target is a contributor on otherUser's journey
+    const otherJourney = createJourney(testDb, otherUser.id);
+    addJourneyContributor(testDb, otherJourney.id, target.id);
+
+    // journey_entries: target authored an entry on otherUser's journey
+    createJourneyEntry(testDb, otherJourney.id, target.id);
+
+    // journey_share_tokens: target created a share token for otherUser's journey
+    testDb.prepare("INSERT INTO journey_share_tokens (journey_id, token, created_by) VALUES (?, 'jst-admin-test', ?)").run(otherJourney.id, target.id);
+
+    // notifications.sender_id (SET NULL): target sent a notification to otherUser
+    const sentNotif = testDb.prepare(
+      "INSERT INTO notifications (type, scope, target, sender_id, recipient_id, title_key, text_key) VALUES ('simple', 'trip', ?, ?, ?, 'k', 'k')"
+    ).run(otherTrip.id, target.id, otherUser.id);
+    // notifications.recipient_id (CASCADE): otherUser sent a notification to target
+    testDb.prepare(
+      "INSERT INTO notifications (type, scope, target, sender_id, recipient_id, title_key, text_key) VALUES ('simple', 'trip', ?, ?, ?, 'k', 'k')"
+    ).run(otherTrip.id, otherUser.id, target.id);
+
+    // user_notice_dismissals (CASCADE): target dismissed a notice
+    testDb.prepare(
+      "INSERT INTO user_notice_dismissals (user_id, notice_id, dismissed_at) VALUES (?, 'test-notice', ?)"
+    ).run(target.id, Date.now());
+
+    const res = await request(app)
+      .delete(`/api/admin/users/${target.id}`)
+      .set('Cookie', authCookie(admin.id));
+    expect(res.status).toBe(200);
+    expect(res.body.success).toBe(true);
+
+    expect(testDb.prepare('SELECT id FROM users WHERE id = ?').get(target.id)).toBeUndefined();
+    // trip_members row survives but invited_by is now NULL
+    expect((testDb.prepare('SELECT invited_by FROM trip_members WHERE trip_id = ? AND user_id = ?').get(otherTrip.id, thirdUser.id) as any).invited_by).toBeNull();
+    expect(testDb.prepare('SELECT id FROM share_tokens WHERE created_by = ?').get(target.id)).toBeUndefined();
+    expect((testDb.prepare('SELECT paid_by_user_id FROM budget_items WHERE id = ?').get(budgetItem.id) as any).paid_by_user_id).toBeNull();
+    expect(testDb.prepare('SELECT user_id FROM journey_contributors WHERE journey_id = ? AND user_id = ?').get(otherJourney.id, target.id)).toBeUndefined();
+    expect(testDb.prepare('SELECT id FROM journey_entries WHERE author_id = ?').get(target.id)).toBeUndefined();
+    expect(testDb.prepare('SELECT id FROM journey_share_tokens WHERE created_by = ?').get(target.id)).toBeUndefined();
+    // sent notification survives but sender_id becomes NULL
+    expect((testDb.prepare('SELECT sender_id FROM notifications WHERE id = ?').get(sentNotif.lastInsertRowid) as any).sender_id).toBeNull();
+    // received notification is cascade-deleted
+    expect(testDb.prepare('SELECT id FROM notifications WHERE recipient_id = ?').get(target.id)).toBeUndefined();
+    // notice dismissals are cascade-deleted
+    expect(testDb.prepare("SELECT user_id FROM user_notice_dismissals WHERE user_id = ? AND notice_id = 'test-notice'").get(target.id)).toBeUndefined();
+  });
+
   it('ADMIN-006 — admin cannot delete their own account', async () => {
     const { user: admin } = createAdmin(testDb);