- Remove `NoSessionPatternUserMessages` constant from `chatter.go`
- Replace direct constant reference with `i18n.T()` translation call
- Update test import from `core` package to `i18n` package
- Update test assertion to use localized error message lookup
### CHANGES
- Introduce `cmd` directory for all main application binaries.
- Move all Go packages into the `internal` directory.
- Rename the `restapi` package to `server` for clarity.
- Consolidate patterns and strategies into a new `data` directory.
- Group all auxiliary scripts into a new `scripts` directory.
- Move all documentation and images into a `docs` directory.
- Update all Go import paths to reflect the new structure.
- Adjust CI/CD workflows and build commands for new layout.
