docs(readme): update README and bump version to 1.6.1

- Remove duplicated --config bullet.
- Update Excel section to reflect production-grade XLSX features.
- Add --no-time note for file formats.
- Add readable API error messaging to feature list.
- Fix development commands: use --check flags and add mypy.
- Replace verbose per-format sections with a summary table.
- Bump pyproject.toml version to 1.6.1.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "redmine-reporter"
-version = "1.6.0"
+version = "1.6.1"
 description = "Redmine time-entry based issue reporter for internal use"
 readme = "README.md"
 authors = [{ name = "Artem Kokos", email = "artem-kokos@mail.ru" }]