feat: YAML config support (~/.config/redmine-reporter/config.yml)

- Add AppConfig/SmtpConfig/EmailConfig dataclasses with from_yaml()/from_env()
- Add yaml_config.py: ${VAR} resolver, 0700/0600 permission helpers
- Config.get_*() methods gain YAML fallback in priority chain
- Priority: CLI > env > .env > YAML > code defaults
- CLI --init-config generates YAML from current environment
- --force flag allows overwriting existing config
- Secrets default to ${VAR} references, plaintext allowed
- Full backward compatibility with existing .env setups

Closes #46

tests/test_cli.py

@@ -18,9 +18,11 @@ def _reset_config_overrides():
 
     Config.set_redmine_url("")
     Config.set_redmine_api_key("")
+    Config._app = None
     yield
     Config.set_redmine_url("")
     Config.set_redmine_api_key("")
+    Config._app = None
 
 
 @pytest.mark.parametrize(
@@ -301,3 +303,93 @@ def test_cli_rejects_multiple_user_flags():
         ]
     )
     assert code == 1
+
+
+# ---------------------------------------------------------------------------
+# --init-config tests
+# ---------------------------------------------------------------------------
+
+
+class TestInitConfig:
+    """Tests for --init-config flag."""
+
+    @mock.patch.dict(os.environ, VALID_ENV, clear=True)
+    def test_init_config_creates_yaml_file(self, tmp_path):
+        """--init-config создаёт YAML файл с правильной структурой."""
+        import yaml
+
+        config_path = tmp_path / "config.yml"
+        code = main(["--init-config", "--config-path", str(config_path)])
+        assert code == 0
+        assert config_path.exists()
+
+        with open(config_path) as fh:
+            data = yaml.safe_load(fh)
+
+        assert "redmine" in data
+        assert data["redmine"]["url"] == "https://red.eltex.loc"
+        assert data["redmine"]["api_key"] == "${REDMINE_API_KEY}"
+
+    @mock.patch.dict(os.environ, VALID_ENV, clear=True)
+    def test_init_config_existing_file_no_force(self, tmp_path, capsys):
+        """Без --force существующий файл → предупреждение и выход 1."""
+        config_path = tmp_path / "config.yml"
+        config_path.write_text("existing: true")
+
+        code = main(["--init-config", "--config-path", str(config_path)])
+        assert code == 1
+        captured = capsys.readouterr()
+        assert "already exists" in captured.err or "already exists" in captured.out
+
+    @mock.patch.dict(os.environ, VALID_ENV, clear=True)
+    def test_init_config_force_overwrites(self, tmp_path):
+        """--init-config --force перезаписывает существующий файл."""
+        import yaml
+
+        config_path = tmp_path / "config.yml"
+        config_path.write_text("existing: true")
+
+        code = main(["--init-config", "--force", "--config-path", str(config_path)])
+        assert code == 0
+
+        with open(config_path) as fh:
+            data = yaml.safe_load(fh)
+
+        assert "redmine" in data
+        assert "existing" not in data
+
+    @mock.patch.dict(os.environ, VALID_ENV, clear=True)
+    def test_init_config_with_date_is_error(self, capsys):
+        """--init-config с --date → ошибка, взаимоисключающие."""
+        code = main(["--init-config", "--date", "2026-01-01--2026-01-31"])
+        assert code == 1
+
+    @mock.patch.dict(os.environ, VALID_ENV, clear=True)
+    def test_init_config_writes_secrets_as_env_ref(self, tmp_path):
+        """Секреты пишутся как ${VAR} когда переменная окружения существует."""
+        import yaml
+
+        config_path = tmp_path / "config.yml"
+        code = main(["--init-config", "--config-path", str(config_path)])
+        assert code == 0
+
+        with open(config_path) as fh:
+            data = yaml.safe_load(fh)
+
+        assert data["redmine"]["api_key"] == "${REDMINE_API_KEY}"
+
+    @mock.patch.dict(os.environ, {}, clear=True)
+    def test_init_config_no_env_vars(self, tmp_path):
+        """Без переменных окружения --init-config создаёт скелет."""
+        import yaml
+
+        config_path = tmp_path / "config.yml"
+        code = main(["--init-config", "--config-path", str(config_path)])
+        assert code == 0
+
+        with open(config_path) as fh:
+            data = yaml.safe_load(fh)
+
+        assert "redmine" in data
+        assert data["redmine"]["url"] == ""
+        assert data["redmine"]["api_key"] == ""