feat(notices): add v3014-whitespace-collision admin notice

Adds a dismissible banner for admins on v3.0.14+ that fires only when
the whitespace-trimming migration detected a username/email collision
(stored in app_settings as whitespace_migration_collision=true).

Notice conditions: existingUserBeforeVersion(3.0.14) + role=admin +
custom predicate reading the app_settings flag. Predicate registered in
registry.ts; migration step writes the flag when hadCollision=true.

All 15 translation files updated with title/body keys.
7 integration tests added (SN-COLLISION-1 through -7) covering all
condition branches: shown when all conditions met, hidden when flag
absent/false, hidden for non-admin, hidden for new user, hidden below
min app version, hidden after dismissal.

server/tests/integration/systemNotices.test.ts

@@ -39,7 +39,7 @@ 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 } from '../helpers/factories';
+import { createUser, createAdmin } from '../helpers/factories';
 import { authCookie } from '../helpers/auth';
 import { SYSTEM_NOTICES } from '../../src/systemNotices/registry';
 import type { SystemNotice } from '../../src/systemNotices/types';
@@ -242,3 +242,129 @@ describe('POST /api/system-notices/:id/dismiss', () => {
     }
   });
 });
+
+// ─────────────────────────────────────────────────────────────────────────────
+// v3014-whitespace-collision notice
+// ─────────────────────────────────────────────────────────────────────────────
+
+/**
+ * Helper: creates an admin user whose first_seen_version is before 3.0.14
+ * (so existingUserBeforeVersion('3.0.14') passes) and whose login_count is
+ * high enough to suppress the firstLogin and v3-upgrade notice conditions.
+ */
+function setupCollisionAdmin() {
+  const { user } = createAdmin(testDb);
+  testDb.prepare('UPDATE users SET login_count = 5, first_seen_version = ? WHERE id = ?').run('3.0.0', user.id);
+  return user;
+}
+
+describe('v3014-whitespace-collision notice', () => {
+  const NOTICE_ID = 'v3014-whitespace-collision';
+  const originalAppVersion = process.env.APP_VERSION;
+
+  beforeEach(() => {
+    process.env.APP_VERSION = '3.0.14';
+  });
+
+  afterEach(() => {
+    if (originalAppVersion === undefined) {
+      delete process.env.APP_VERSION;
+    } else {
+      process.env.APP_VERSION = originalAppVersion;
+    }
+  });
+
+  it('SN-COLLISION-1 — shown to admin when collision flag is set and user predates 3.0.14', async () => {
+    const user = setupCollisionAdmin();
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'true')").run();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeDefined();
+  });
+
+  it('SN-COLLISION-2 — hidden when collision flag is absent', async () => {
+    const user = setupCollisionAdmin();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+
+  it('SN-COLLISION-3 — hidden when collision flag is explicitly false', async () => {
+    const user = setupCollisionAdmin();
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'false')").run();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+
+  it('SN-COLLISION-4 — hidden for non-admin user even when collision flag is set', async () => {
+    const { user } = createUser(testDb);
+    testDb.prepare('UPDATE users SET login_count = 5, first_seen_version = ? WHERE id = ?').run('3.0.0', user.id);
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'true')").run();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+
+  it('SN-COLLISION-5 — hidden for user whose first_seen_version is >= 3.0.14 (new account)', async () => {
+    const { user } = createAdmin(testDb);
+    testDb.prepare('UPDATE users SET login_count = 5, first_seen_version = ? WHERE id = ?').run('3.0.14', user.id);
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'true')").run();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+
+  it('SN-COLLISION-6 — hidden when app version is below 3.0.14', async () => {
+    process.env.APP_VERSION = '3.0.13';
+    const user = setupCollisionAdmin();
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'true')").run();
+
+    const res = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+
+    expect(res.status).toBe(200);
+    expect(res.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+
+  it('SN-COLLISION-7 — hidden after admin dismisses it', async () => {
+    const user = setupCollisionAdmin();
+    testDb.prepare("INSERT OR REPLACE INTO app_settings (key, value) VALUES ('whitespace_migration_collision', 'true')").run();
+
+    const before = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+    expect(before.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeDefined();
+
+    const dismiss = await request(app)
+      .post(`/api/system-notices/${NOTICE_ID}/dismiss`)
+      .set('Cookie', authCookie(user.id));
+    expect(dismiss.status).toBe(204);
+
+    const after = await request(app)
+      .get('/api/system-notices/active')
+      .set('Cookie', authCookie(user.id));
+    expect(after.body.find((n: { id: string }) => n.id === NOTICE_ID)).toBeUndefined();
+  });
+});