feat: implement performance instrumentation v2

[aviralgarg05]

Related Issue

Closes #911

Description

This PR implements comprehensive performance instrumentation across the Eigent backend and Electron startup process. It introduces a centralized PerfTimer utility to capture execution durations and log them with context, enabling better bottleneck identification and observability.

Key Changes:

1. Instrumentation Utility: Created backend/app/utils/perf_timer.py providing the PerfTimer context manager and @perf_measure decorator using standard Python logging.
2. Agent & Workforce Instrumentation:
   • chat_service.py: Instrumented session start, workforce construction, and task decomposition.
   • workforce.py: Instrumented the high-level task decomposition and workforce start logic.
   • single_agent_worker.py: Instrumented overall task processing and specific agent steps.
   • listen_chat_agent.py: Instrumented both synchronous and asynchronous agent steps and tool executions.
3. Startup Performance:
   • backend/main.py: Added module load timing.
   • electron/main/init.ts: Instrumented the backend spawn process and health check duration.
4. Testing: Added backend/tests/unit/utils/test_perf_timer.py with 19 test cases covering sync/async usage and exception handling.

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Contribution Guidelines Acknowledgement

• I have read and agree to the Eigent Contribution Guideline

[Wendong-Fan]

thanks @aviralgarg05 , could you share a sample PerfTimer output so we can analyze the current performance bottlenecks?