fix(tests): resolve 4 failing test suites and patch lodash vulnerability

Test fixes (type mismatches introduced by V&V resolution changes):
- HealthDetailedController.test.ts: replace pool/makePool with dbProbe/makeDbProbe
  to match refactored HealthDetailedDeps interface (Pool → DbProbe abstraction)
- EventPublisher.test.ts: pass all 4 required constructor args to WebhookDeliveryWorker
  mock (pool, vaultClient, redisClient, redisUrl) — was passing only 1
- MarketplaceService.test.ts: IAgent.did/didCreatedAt are string|undefined (not null);
  fix makeAgent defaults and makeAgent({did:null}) call; fix type assertion to unknown first
- OIDCTrustPolicyService.test.ts: ICreateTrustPolicyRequest.branch is string|undefined
  (not nullable); replace all branch:null with branch:undefined

Security fix:
- npm audit fix: lodash ≤4.17.23 (HIGH) → patched; 0 vulnerabilities remaining

Result: 50/50 test suites pass, 722/722 tests pass, 0 vulnerabilities

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/services/MarketplaceService.test.ts

@@ -27,8 +27,8 @@ function makeAgent(overrides: Partial<IAgent> = {}): IAgent {
     isPublic: true,
     createdAt: new Date('2026-01-01'),
     updatedAt: new Date('2026-01-02'),
-    did: null,
-    didCreatedAt: null,
+    did: undefined,
+    didCreatedAt: undefined,
     ...overrides,
   };
 }
@@ -62,7 +62,7 @@ describe('MarketplaceService', () => {
       agentRepo.findPublicAgents = jest.fn().mockResolvedValue({ agents: [agent], total: 1 });
 
       const result = await service.listPublicAgents(BASE_FILTERS);
-      const card = result.data[0] as Record<string, unknown>;
+      const card = result.data[0] as unknown as Record<string, unknown>;
 
       expect(card['email']).toBeUndefined();
       expect(card['organizationId']).toBeUndefined();
@@ -79,7 +79,7 @@ describe('MarketplaceService', () => {
     });
 
     it('should return null DID document when agent has no DID', async () => {
-      const agent = makeAgent({ did: null });
+      const agent = makeAgent({ did: undefined });
       agentRepo.findPublicAgents = jest.fn().mockResolvedValue({ agents: [agent], total: 1 });
 
       const result = await service.listPublicAgents(BASE_FILTERS);