feat(#175): Implement E2E test harness

- Create comprehensive E2E test suite for job orchestration
- Add test fixtures for Discord, BullMQ, and Prisma mocks
- Implement 9 end-to-end test scenarios covering:
  * Happy path: webhook → job → step execution → completion
  * Event emission throughout job lifecycle
  * Step failure and retry handling
  * Job failure after max retries
  * Discord command parsing and job creation
  * WebSocket status updates integration
  * Job cancellation workflow
  * Job retry mechanism
  * Progress percentage tracking

- Add helper methods to services for simplified testing:
  * JobStepsService: start(), complete(), fail(), findByJob()
  * RunnerJobsService: updateStatus(), updateProgress()
  * JobEventsService: findByJob()

- Configure vitest.e2e.config.ts for E2E test execution
- All 9 E2E tests passing
- All 1405 unit tests passing
- Quality gates: typecheck, lint, build all passing

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/test/fixtures/mock-bullmq.fixture.ts

@@ -0,0 +1,83 @@
+import { vi } from "vitest";
+import type { Queue, Job } from "bullmq";
+
+/**
+ * Mock BullMQ job for testing
+ */
+export function createMockBullMqJob(overrides?: Partial<Job>): Partial<Job> {
+  return {
+    id: "mock-bull-job-id",
+    name: "runner-job",
+    data: {
+      jobId: "mock-job-id",
+      workspaceId: "mock-workspace-id",
+      type: "code-task",
+    },
+    progress: vi.fn().mockReturnValue(0),
+    updateProgress: vi.fn().mockResolvedValue(undefined),
+    log: vi.fn().mockResolvedValue(undefined),
+    remove: vi.fn().mockResolvedValue(undefined),
+    ...overrides,
+  };
+}
+
+/**
+ * Mock BullMQ queue for testing
+ */
+export function createMockBullMqQueue(): Partial<Queue> {
+  const jobs = new Map<string, Partial<Job>>();
+
+  return {
+    add: vi.fn().mockImplementation((name: string, data: unknown) => {
+      const job = createMockBullMqJob({
+        id: `job-${Date.now()}`,
+        name,
+        data: data as never,
+      });
+      jobs.set(job.id as string, job);
+      return Promise.resolve(job);
+    }),
+    getJob: vi.fn().mockImplementation((jobId: string) => {
+      return Promise.resolve(jobs.get(jobId) || null);
+    }),
+    getJobs: vi.fn().mockResolvedValue([]),
+    pause: vi.fn().mockResolvedValue(undefined),
+    resume: vi.fn().mockResolvedValue(undefined),
+    clean: vi.fn().mockResolvedValue([]),
+    close: vi.fn().mockResolvedValue(undefined),
+    on: vi.fn(),
+    once: vi.fn(),
+  };
+}
+
+/**
+ * Mock BullMQ service for testing
+ */
+export function createMockBullMqService() {
+  const queues = new Map<string, Partial<Queue>>();
+
+  return {
+    addJob: vi
+      .fn()
+      .mockImplementation((queueName: string, jobName: string, data: unknown, opts?: unknown) => {
+        let queue = queues.get(queueName);
+        if (!queue) {
+          queue = createMockBullMqQueue();
+          queues.set(queueName, queue);
+        }
+        return queue.add?.(jobName, data, opts as never);
+      }),
+    getQueue: vi.fn().mockImplementation((queueName: string) => {
+      let queue = queues.get(queueName);
+      if (!queue) {
+        queue = createMockBullMqQueue();
+        queues.set(queueName, queue);
+      }
+      return queue;
+    }),
+    getJob: vi.fn().mockImplementation((queueName: string, jobId: string) => {
+      const queue = queues.get(queueName);
+      return queue?.getJob?.(jobId);
+    }),
+  };
+}