feat: auto-email sending via SMTP (--send flag)

Closes #45

- New redmine_reporter/mailer.py: SMTP email sending with
  {author}/{period} template substitution, MIME attachment
  with correct content-type per file extension
- Config.get_email_config(): returns EmailConfig from YAML
  or None when not configured
- CLI --send flag: sends report after generation, works with
  --output, --commit, or standalone (saves to template path)
- 31 new tests (22 mailer + 6 CLI + 3 config)
- 249/249 tests passing, ruff clean, mypy clean

tests/test_config.py

@@ -557,3 +557,53 @@ class TestDefaultDateRangeWithLastUsed:
             Config._app = AppConfig.from_yaml(yaml_path)
             result = Config.get_default_date_range()
             assert result == "2026-04-01--2026-04-15"
+
+
+class TestGetEmailConfig:
+    """Tests for Config.get_email_config()."""
+
+    @mock.patch.dict(os.environ, {}, clear=True)
+    def test_get_email_config_from_yaml(self):
+        """get_email_config() возвращает EmailConfig из YAML."""
+        with tempfile.TemporaryDirectory() as tmp:
+            yaml_path = Path(tmp) / "config.yml"
+            yaml_path.write_text(
+                "email:\n"
+                "  smtp:\n"
+                "    host: smtp.example.com\n"
+                "    port: 587\n"
+                "    user: bot@example.com\n"
+                "    password: secret\n"
+                "    tls: true\n"
+                "  from: bot@example.com\n"
+                "  to:\n"
+                "    - boss@example.com\n"
+            )
+
+            Config._app = AppConfig.from_yaml(yaml_path)
+            cfg = Config.get_email_config()
+
+            assert cfg is not None
+            assert cfg.smtp.host == "smtp.example.com"
+            assert cfg.smtp.port == 587
+            assert cfg.smtp.user == "bot@example.com"
+            assert cfg.smtp.password == "secret"
+            assert cfg.smtp.tls is True
+            assert cfg.from_ == "bot@example.com"
+            assert cfg.to == ["boss@example.com"]
+
+    @mock.patch.dict(os.environ, {}, clear=True)
+    def test_get_email_config_returns_none_when_no_yaml(self):
+        """Без YAML-конфига get_email_config() возвращает None."""
+        Config._app = None
+        assert Config.get_email_config() is None
+
+    @mock.patch.dict(os.environ, {}, clear=True)
+    def test_get_email_config_returns_none_when_no_host(self):
+        """С YAML но без smtp.host — возвращает None."""
+        with tempfile.TemporaryDirectory() as tmp:
+            yaml_path = Path(tmp) / "config.yml"
+            yaml_path.write_text("email:\n  smtp:\n    host: ''\n")
+
+            Config._app = AppConfig.from_yaml(yaml_path)
+            assert Config.get_email_config() is None