Release v1.6.9
docs: Update README.md to reflect x86_64 (amd64) architecture support only
- Remove outdated ARM64 architecture references from installation instructions
- Update all package filenames to reflect current unified naming format
- Clarify that the application is built for Linux Desktop x86_64 systems only
- Update download links and installation examples with correct filenames
- Remove multi-architecture installation instructions
- Update CHANGELOG.md with v1.6.9 release notes
This ensures documentation matches the current x86_64-only release strategy.