Security: Fix dependency vulnerabilities

- Fix 22 npm vulnerabilities (1 critical, 7 high, 8 moderate, 6 low)
  - Updated Electron to latest version (^38.3.0)
  - Added webpack-dev-server override to fix remaining vulnerabilities
  - All npm vulnerabilities resolved

- Pin Python dependencies to specific versions in requirements.txt
  - fastapi==0.119.0
  - uvicorn==0.38.0
  - python-multipart==0.0.20
  - neuroglancer==2.38
  - imageio==2.37.0
  - tensorboard==2.20.0
  - tensorboard-data-server==0.7.2
  - No Python security vulnerabilities found

Author: akgohain