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.

server/routes/admin.py

@@ -6,6 +6,17 @@ import logging
 
 from .. import auth, settings
 from ..database import delete_app_setting, get_app_settings, get_subscribers, update_app_setting
+from ..services.email_settings import (
+    EMAIL_SETTINGS_DEFINITIONS,
+    load_email_settings,
+    persist_email_settings,
+    validate_email_settings,
+)
+from ..services.email_templates import (
+    list_templates as list_email_templates,
+    load_template as load_email_template,
+    persist_template as persist_email_template,
+)
 
 bp = Blueprint("admin", __name__, url_prefix="/admin")
 
@@ -96,6 +107,13 @@ def email_templates():
     return render_template('admin/admin_email_templates.html')
 
 
+@bp.route('/email-settings')
+@auth.login_required
+def email_settings_page():
+    """Render the dedicated email settings management page."""
+    return render_template('admin/admin_email_settings.html')
+
+
 @bp.route("/api/settings", methods=["GET"])
 @auth.login_required
 def get_settings_api():
@@ -179,6 +197,121 @@ def delete_setting_api(key: str):
         return jsonify({"status": "error", "message": "Failed to delete setting."}), 500
 
 
+@bp.route("/api/email-settings", methods=["GET"])
+@auth.login_required
+def get_email_settings_api():
+    """Return the current email settings with field metadata."""
+    try:
+        data = load_email_settings()
+        return jsonify({
+            "status": "ok",
+            "settings": data,
+            "schema": EMAIL_SETTINGS_DEFINITIONS,
+        })
+    except Exception as exc:  # pragma: no cover - logged and surfaced to client
+        logging.exception("Failed to load email settings: %s", exc)
+        return jsonify({
+            "status": "error",
+            "message": "Failed to load email settings."
+        }), 500
+
+
+@bp.route("/api/email-settings", methods=["PUT"])
+@auth.login_required
+def update_email_settings_api():
+    """Validate and persist email settings updates."""
+    try:
+        payload = request.get_json(silent=True) or {}
+        errors = validate_email_settings(payload)
+        if errors:
+            return jsonify({
+                "status": "error",
+                "message": "Email settings validation failed.",
+                "errors": errors,
+            }), 400
+
+        updated = persist_email_settings(payload)
+        return jsonify({
+            "status": "ok",
+            "message": "Email settings updated successfully.",
+            "settings": updated,
+        })
+    except Exception as exc:  # pragma: no cover - logged and surfaced to client
+        logging.exception("Failed to update email settings: %s", exc)
+        return jsonify({
+            "status": "error",
+            "message": "Failed to update email settings."
+        }), 500
+
+
+@bp.route("/api/email-templates", methods=["GET"])
+@auth.login_required
+def list_email_templates_api():
+    """Return metadata for editable email templates."""
+    try:
+        templates = list_email_templates()
+        return jsonify({"status": "ok", "templates": templates})
+    except Exception as exc:  # pragma: no cover
+        logging.exception("Failed to list email templates: %s", exc)
+        return jsonify({
+            "status": "error",
+            "message": "Failed to load email templates."
+        }), 500
+
+
+@bp.route("/api/email-templates/<template_id>", methods=["GET"])
+@auth.login_required
+def get_email_template_api(template_id: str):
+    """Return the requested email template."""
+    try:
+        template = load_email_template(template_id)
+        return jsonify({"status": "ok", "template": template})
+    except KeyError:
+        return jsonify({
+            "status": "error",
+            "message": "Email template not found."
+        }), 404
+    except Exception as exc:  # pragma: no cover
+        logging.exception(
+            "Failed to load email template %s: %s", template_id, exc)
+        return jsonify({
+            "status": "error",
+            "message": "Failed to load email template."
+        }), 500
+
+
+@bp.route("/api/email-templates/<template_id>", methods=["PUT"])
+@auth.login_required
+def update_email_template_api(template_id: str):
+    """Persist updates to an email template."""
+    try:
+        payload = request.get_json(silent=True) or {}
+        content = payload.get("content", "")
+        if not isinstance(content, str) or not content.strip():
+            return jsonify({
+                "status": "error",
+                "message": "Template content is required.",
+            }), 400
+
+        updated = persist_email_template(template_id, content)
+        return jsonify({
+            "status": "ok",
+            "template": updated,
+        })
+    except KeyError:
+        return jsonify({
+            "status": "error",
+            "message": "Email template not found."
+        }), 404
+    except Exception as exc:  # pragma: no cover
+        logging.exception(
+            "Failed to update email template %s: %s", template_id, exc)
+        return jsonify({
+            "status": "error",
+            "message": "Failed to update email template."
+        }), 500
+
+
 @bp.route("/api/newsletter", methods=["GET"])
 @auth.login_required
 def get_subscribers_api():