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/vitest.e2e.config.ts

@@ -0,0 +1,33 @@
+import swc from "unplugin-swc";
+import { defineConfig } from "vitest/config";
+import path from "path";
+
+export default defineConfig({
+  test: {
+    globals: false,
+    environment: "node",
+    include: ["test/e2e/**/*.e2e-spec.ts"],
+    coverage: {
+      provider: "v8",
+      reporter: ["text", "json", "html"],
+      exclude: ["node_modules/", "dist/", "test/"],
+    },
+    testTimeout: 30000, // E2E tests may take longer
+    hookTimeout: 30000,
+    server: {
+      deps: {
+        inline: ["@nestjs/common", "@nestjs/core"],
+      },
+    },
+  },
+  resolve: {
+    alias: {
+      "@": path.resolve(__dirname, "./src"),
+    },
+  },
+  plugins: [
+    swc.vite({
+      module: { type: "es6" },
+    }),
+  ],
+});