feat: Add email settings management and templates functionality

- Implemented email settings configuration in the admin panel, allowing for SMTP settings and notification preferences.
- Created a new template for email settings with fields for SMTP host, port, username, password, sender address, and recipients.
- Added JavaScript functionality to handle loading, saving, and validating email settings.
- Introduced email templates management, enabling the listing, editing, and saving of email templates.
- Updated navigation to include links to email settings and templates.
- Added tests for email settings and templates to ensure proper functionality and validation.

tests/test_email_templates_service.py

@@ -0,0 +1,44 @@
+from __future__ import annotations
+
+from typing import Any
+
+import pytest
+
+from server.services import email_templates
+
+
+def test_list_templates_returns_metadata():
+    templates = email_templates.list_templates()
+    assert isinstance(templates, list)
+    assert templates[0]["id"] == "newsletter_confirmation"
+    assert "name" in templates[0]
+
+
+def test_load_template_uses_default_when_not_stored(monkeypatch):
+    monkeypatch.setattr(email_templates, "get_app_settings", lambda: {})
+    template = email_templates.load_template("newsletter_confirmation")
+    assert template["content"] == email_templates.EMAIL_TEMPLATE_DEFINITIONS[
+        "newsletter_confirmation"
+    ].default_content
+
+
+def test_persist_template_updates_storage(monkeypatch):
+    captured: dict[str, Any] = {}
+
+    def fake_update(key: str, value: str) -> None:
+        captured["key"] = key
+        captured["value"] = value
+
+    # Return content via load call after persist
+    monkeypatch.setattr(email_templates, "update_app_setting", fake_update)
+    monkeypatch.setattr(
+        email_templates,
+        "get_app_settings",
+        lambda: {"newsletter_confirmation_template": "stored"},
+    )
+
+    updated = email_templates.persist_template(
+        "newsletter_confirmation", " stored ")
+    assert captured["key"] == "newsletter_confirmation_template"
+    assert captured["value"] == "stored"
+    assert updated["content"] == "stored"