Update manifest.json with new file metadata and add pytest configuration

- Updated timestamps and AST hashes for multiple files in the manifest.json.
- Added new test file backend/tests/test_expected_income.py.
- Added documentation files: перево́д_между_своими.md and 0002-fixes.md.
- Introduced pytest.ini to configure pytest settings, including test paths and warning filters.

pytest.ini

@@ -0,0 +1,8 @@
+[pytest]
+pythonpath = backend
+testpaths = backend/tests
+addopts = -m "not private_fixtures"
+markers =
+    private_fixtures: real-statement private suite; run explicitly with -m private_fixtures
+filterwarnings =
+    ignore::DeprecationWarning