feat(#174): Implement SSE endpoint for CLI consumers

Add Server-Sent Events (SSE) endpoint for streaming job events to CLI
consumers who prefer HTTP streaming over WebSocket.

Endpoint: GET /runner-jobs/:id/events/stream

Features:
- Database polling (500ms interval) for new events
- Keep-alive pings (15s interval) to prevent timeout
- Auto-cleanup on connection close or job completion
- Authentication required (workspace member)
- SSE format: event: <type>\ndata: <json>\n\n

Implementation:
- Added streamEvents method to RunnerJobsService
- Added streamEvents endpoint to RunnerJobsController
- Comprehensive unit tests for both controller and service
- All quality gates pass (typecheck, lint, build, test)

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

apps/api/src/runner-jobs/runner-jobs.controller.spec.ts

@@ -297,9 +297,7 @@ describe("RunnerJobsController", () => {
       await controller.streamEvents(jobId, workspaceId, mockRes as never);
 
       // Verify error is written to stream
-      expect(mockRes.write).toHaveBeenCalledWith(
-        expect.stringContaining("Job not found")
-      );
+      expect(mockRes.write).toHaveBeenCalledWith(expect.stringContaining("Job not found"));
       expect(mockRes.end).toHaveBeenCalled();
     });
   });