feat(tests): add comprehensive unit test suite (v1.4.0)

- Add 38 unit tests covering fw_client, recipes, lists, and server modules
- Test error handling: top-level ex/un, nested a00.un.un/a00.ex.ex, successful responses
- Test ingredients_parsed parser: newlines, empty lines, commas, headings
- Test list name translation: SYS-CAT-SHOPPINGLIST, SYS-CAT-TODOS, unknown names
- Test date validation: ISO YYYY-MM-DD format enforcement
- Test error response helper: JSON format, Unicode, special characters
- All tests use unittest.mock (stdlib), no external mocking libraries
- No API calls — all HTTP interactions mocked
- Framework: pytest with asyncio support
- Run: uv run pytest tests/test_unit.py -v

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -10,6 +10,23 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 This project follows Semantic Versioning (SemVer).
 Breaking changes (removed tools, changed parameters) increment the major version.
 
+## [1.4.0] – 2026-04-17
+
+### Added
+- **Unit test suite** (`tests/test_unit.py`) — comprehensive tests for core modules
+  - `fw_client.py`: Error handling (top-level `ex`/`un`, nested `a00.un.un`/`a00.ex.ex`, successful responses)
+  - `recipes.py`: `ingredients_parsed` parser (newline handling, empty lines, headings, commas)
+  - `lists.py`: System list name translation (SYS-CAT-SHOPPINGLIST, SYS-CAT-TODOS, unknown names)
+  - `server.py`: `_validate_date()` (ISO YYYY-MM-DD validation, format errors)
+  - `server.py`: `_err()` helper (JSON response format, Unicode, special characters)
+- All tests use `unittest.mock` (stdlib, no external dependencies)
+- Tests run without API access; all HTTP calls are mocked
+- Framework: pytest with asyncio support
+
+### Notes
+- Run tests: `uv run pytest tests/test_unit.py -v`
+- No breaking changes; release is testing infrastructure only
+
 ## [1.3.1] – 2026-04-17
 
 ### Fixed