refactor(server): remove DatabaseService.transaction — every transaction runs through UnitOfWork

server/src/nest/README.md

@@ -914,8 +914,9 @@ cycle seams are folded, nothing on the websocket path imports one, and the
 crons all inject now (`*.job.ts` providers on `scheduling/CronRegistrarService`).
 
 1. **Move the SQL** into `<domain>.service.ts` as methods over an injected
-   `DatabaseService` (`this.db.all<T>/get<T>/run/prepare/transaction`; strict
-   constructor injection, no `@Optional()`). Preserve every quirk: falsy-coercion
+   `DatabaseService` (`this.db.all<T>/get<T>/run/prepare`; multi-statement writes go
+   through `await this.uow.transactional(...)` instead — see the root `CLAUDE.md`;
+   strict constructor injection, no `@Optional()`). Preserve every quirk: falsy-coercion
    defaults (`x || fallback`, never `??`), post-insert/post-update re-selects (no
    RETURNING), `COALESCE` semantics. If a controller already wraps the legacy
    functions, do not change the service's method surface. The module needs no

server/src/nest/database/database.service.ts

@@ -38,11 +38,6 @@ export class DatabaseService {
     return this.conn.prepare(sql).run(...params);
   }
 
-  /** Run `fn` inside a synchronous better-sqlite3 transaction. */
-  transaction<T>(fn: (conn: Database.Database) => T): T {
-    return this.conn.transaction(() => fn(this.conn))();
-  }
-
   // Trip-access helpers delegate to the db/database exports (not this.conn):
   // tests vi.mock that module and stub the helpers themselves, so the stubs
   // must keep flowing through here.

server/tests/unit/nest/database-service.test.ts

@@ -19,18 +19,15 @@ describe('DatabaseService (typed query helpers)', () => {
     expect(svc.all('SELECT 3 AS three')).toEqual([{ three: 3 }]);
   });
 
-  it('run + transaction operate on a scratch table', () => {
+  it('run operates on a scratch table', () => {
     svc.run('CREATE TEMP TABLE IF NOT EXISTS _dbsvc_test (n INTEGER)');
     svc.run('DELETE FROM _dbsvc_test');
 
     const info = svc.run('INSERT INTO _dbsvc_test (n) VALUES (?)', 41);
     expect(info.changes).toBe(1);
 
-    const total = svc.transaction((conn) => {
-      conn.prepare('INSERT INTO _dbsvc_test (n) VALUES (?)').run(1);
-      return conn.prepare('SELECT SUM(n) AS s FROM _dbsvc_test').get() as { s: number };
-    });
-    expect(total.s).toBe(42);
+    const total = svc.get('SELECT SUM(n) AS s FROM _dbsvc_test') as { s: number };
+    expect(total.s).toBe(41);
 
     svc.run('DROP TABLE _dbsvc_test');
   });

server/tests/unit/nest/google-route.test.ts

@@ -13,7 +13,7 @@ const routeTestDb = new Database(':memory:');
 
 async function setup() {
   const maps = { geocodeQuery: vi.fn(), reverseGeocode: vi.fn().mockResolvedValue({ name: null, address: null }) };
-  const db = { canAccessTrip: vi.fn(() => ({ user_id: 7 })), get: () => ({ role: 'user' }), transaction: <T>(fn: () => T) => fn() };
+  const db = { canAccessTrip: vi.fn(() => ({ user_id: 7 })), get: () => ({ role: 'user' }) };
   const places = { create: vi.fn((_trip: string, stop: { name: string }) => ({ id: stop.name })), broadcast: vi.fn() };
   const assignments = { dayExists: vi.fn(() => true), createAssignment: vi.fn((dayId: number, placeId: string) => ({ dayId, placeId })), broadcast: vi.fn(), reconcile: vi.fn() };
   const permissions = { checkPermission: vi.fn(() => true) };

server/tests/unit/nest/roadtrip-planning.test.ts

@@ -40,7 +40,6 @@ function setup() {
     run: vi.fn((_sql: string, tripId: number, key: string, value: string) =>
       tripSettings.set(tripId, { ...tripSettings.get(tripId), [key]: JSON.parse(value) }),
     ),
-    transaction: (fn: () => unknown) => fn(),
   };
   const preferences = new RoadtripPreferencesService(preferenceDb as never, realtime as never, uowStub);
   const days = [{ id: 1, day_number: 1, title: null, date: '2026-09-11', default_transport_mode: 'driving' }];

server/tests/unit/nest/roadtrip.service.test.ts

@@ -42,7 +42,6 @@ async function makeService() {
     get: <T>(sql: string, ...params: unknown[]) => raw.prepare(sql).get(...params as never[]) as T | undefined,
     all: <T>(sql: string, ...params: unknown[]) => raw.prepare(sql).all(...params as never[]) as T[],
     run: (sql: string, ...params: unknown[]) => raw.prepare(sql).run(...params as never[]),
-    transaction: <T>(fn: (conn: unknown) => T) => raw.transaction(() => fn(raw))(),
   };
   // The realtime side is exercised through the controller and the MCP layer; here the
   // service is under test for what it writes, so a broadcast that goes nowhere is right.