test(server): src/config takes fixed test values from the setup file, so suites stop mocking it

tests/setup.ts mocks src/config once with tests/helpers/test-config.ts. A suite that needs other values calls overrideTestConfig(), and the setup file restores the defaults after every case. The 191 per-file factories are gone; config.test.ts takes the real module through vi.unmock, and the few suites that signed tokens with their own literal secret read it from TEST_CONFIG.

server/tests/unit/nest/admin.version-notification.test.ts

@@ -27,12 +27,6 @@ vi.mock('../../../src/db/database', async () => {
     return mock;
 });
 
-
-vi.mock('../../../src/config', () => ({
-  JWT_SECRET: 'test-jwt-secret-for-trek-testing-only',
-  ENCRYPTION_KEY: 'a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6a7b8c9d0e1f2a3b4c5d6a7b8c9d0e1f2',
-  updateJwtSecret: () => {},
-}));
 vi.mock('../../../src/websocket', () => ({ broadcastToUser: vi.fn() }));
 // Mock MCP to avoid session side-effects
 vi.mock('../../../src/mcp', () => ({ revokeUserSessions: vi.fn(), invalidateMcpSessions: vi.fn() }));