feat: add hypeman build command (#21)

Add a new 'build' command that builds images from a Dockerfile and source context.

Features:
- Takes a folder path as the build context (default: current directory)
- Optionally accepts a Dockerfile path via --file/-f flag
- Creates a tar.gz archive of the source and uploads via multipart form
- Streams build logs in real-time via SSE
- Configurable build timeout via --timeout flag (default: 600s)

Usage examples:
  hypeman build
  hypeman build ./myapp
  hypeman build -f Dockerfile.prod ./myapp
  hypeman build --timeout 1200 ./myapp

Author: hiroTamada