Step 22b/23 (Phase 6): Release — Create CHANGELOG.md + CI release workflow

[Jordan231111]

Summary

Create a CHANGELOG following Keep a Changelog format and set up the CI release workflow that builds cross-platform binaries on tag push.

Depends On: Step 22a (Release scripts)
Parent Issue: #14 (Final Release Preparation)

Key Changes

1. Create `CHANGELOG.md`:
   • Follow Keep a Changelog format
   • Document all v1.0.0 features: scan, quarantine, remove, update-db, deep scan, hash
   • Sections: Added, Changed, Fixed, Security
   • Include links to relevant issues/PRs
2. Create/update CI release workflow (`.github/workflows/release.yml`):
   • Trigger on tag push matching `v*`
   • Matrix strategy: ubuntu-latest, macos-latest, windows-latest
   • Steps: checkout → toolchain → build release → generate checksum → upload artifact
   • Upload artifacts to GitHub Release (auto-created from tag)
   • Each platform artifact includes: binary + SHA-256 checksum file
   • Pin all actions to commit SHAs
3. Release naming: `malware-minimizer--.tar.gz` (Unix), `.zip` (Windows)

Acceptance Criteria

• CHANGELOG.md follows Keep a Changelog format with all v1.0.0 changes
• CI release workflow triggers on tag push
• Cross-platform builds produce binaries for Linux, macOS, Windows
• Per-platform SHA-256 checksums are generated and uploaded
• Artifacts are uploaded to GitHub Releases
• Actions are pinned to commit SHAs
• Release workflow is fully automated from tag push to published release