Fix SIGILL crash on CPUs without AVX2 support

[sgasser]

Summary

Fixes #70 - PasteGuard crashes with SIGILL on x86_64 CPUs without AVX2 support (e.g., Intel Atom C3558R).

Root cause: The Bun install script detected AVX2 on the GitHub Actions build host and installed the optimized binary. When run on CPUs without AVX2, it crashed immediately.

Fix: Copy the Bun binary directly from the official oven/bun:1-slim builder stage. The official images use baseline builds for x64, which only require SSE4.2.

Also fixes compatibility with the updated presidio-analyzer base image which now runs as non-root user.

Changes

• docker/Dockerfile:

  • Copy Bun from builder stage instead of using install script
  • Add USER root for apt-get commands
  • Fix Presidio config paths (/app/presidio_analyzer/conf/)
  • Move PasteGuard to /pasteguard to avoid directory conflict with Presidio

• docker/supervisord.conf:

  • Update Presidio directory to /app
  • Update PasteGuard directory to /pasteguard
  • Update Bun path to /usr/local/bin/bun

Tested

• Docker image builds successfully
• Both Presidio and PasteGuard services start correctly
• Health endpoint returns 200