feat(newsletter): Add subscription confirmation email functionality

- Implemented `send_subscription_confirmation` function to send a confirmation email upon subscription.
- Added a default HTML template for the confirmation email in settings.
- Updated the newsletter management page to handle subscription and unsubscription actions.
- Created new templates for embedding contact and newsletter forms.
- Added styles for the new templates and unified CSS styles across the application.
- Updated tests to reflect changes in the newsletter management API endpoints.

server/routes/newsletter.py

@@ -7,10 +7,10 @@ from flask import Blueprint, jsonify, request, render_template
 
 from ..services import newsletter
 
-bp = Blueprint("newsletter", __name__, url_prefix="/api")
+bp = Blueprint("newsletter", __name__)
 
 
-@bp.route("/newsletter", methods=["POST"])
+@bp.route("/api/newsletter", methods=["POST"])
 def subscribe():
     payload = request.form or request.get_json(silent=True) or {}
     email = (payload.get("email") or "").strip()
@@ -29,10 +29,16 @@ def subscribe():
         return jsonify({"status": "error", "message": "Email is already subscribed."}), 409
 
     logging.info("New newsletter subscription: %s", email)
+
+    # Send confirmation email
+    email_sent = newsletter.send_subscription_confirmation(email)
+    if not email_sent:
+        logging.warning("Confirmation email not sent for %s", email)
+
     return jsonify({"status": "ok", "message": "Subscribed successfully."}), 201
 
 
-@bp.route("/newsletter", methods=["DELETE"])
+@bp.route("/api/newsletter", methods=["DELETE"])
 def unsubscribe():
     payload = request.form or request.get_json(silent=True) or {}
     email = (payload.get("email") or "").strip()
@@ -55,7 +61,7 @@ def unsubscribe():
     return jsonify({"status": "ok", "message": "Unsubscribed successfully."}), 200
 
 
-@bp.route("/newsletter", methods=["PUT"])
+@bp.route("/api/newsletter", methods=["PUT"])
 def update_subscription():
     payload = request.form or request.get_json(silent=True) or {}
     old_email = (payload.get("old_email") or "").strip()
@@ -104,8 +110,7 @@ def manage_subscription():
                 elif action == "unsubscribe":
                     deleted = newsletter.unsubscribe(email)
                     if deleted:
-                        message = "Successfully unsubscribed from newsletter."
-                        message_type = "success"
+                        return render_template("unsubscribe_confirmation.html")
                     else:
                         message = "This email is not currently subscribed."
                         message_type = "info"
@@ -131,3 +136,9 @@ def manage_subscription():
                 message_type = "error"
 
     return render_template("newsletter_manage.html", message=message, message_type=message_type)
+
+
+@bp.route("/newsletter/unsubscribe/confirmation", methods=["GET"])
+def unsubscribe_confirmation():
+    """Display newsletter unsubscription confirmation page."""
+    return render_template("unsubscribe_confirmation.html")