P3: Release process + CHANGELOG + docs enforcement

[Kinin-Code-Offical]

The project needs a documented and automated release process.

Acceptance Criteria:

• Create a CHANGELOG.md file.
• Create a
  elease.yml GitHub Actions workflow that triggers on tags (e.g., �*..).
• The release workflow should build the Flutter Android app (AAB/APK) and create a GitHub Release with the artifacts.
• The main README.md must be updated to be the single source of truth for setup, development, and testing.