feat: Add Swagger API documentation

This commit introduces Swagger API documentation for all endpoints in the
application.

- Installs  and .
- Configures Swagger in  to generate and serve API documentation
  at .
- Adds JSDoc-style Swagger annotations to all routes in  and
  the  directory (, , ,
  , , ).
- Defines a cookie-based security scheme for authenticated routes.

This allows for interactive API documentation and testing via the
endpoint.

routes/payments.js

@@ -39,6 +39,13 @@ DB.getDB.then((DB) => {
     //     });
     // });  
 
+    /**
+ * @swagger
+ * tags:
+ *   name: Payments
+ *   description: Payment processing
+ */
+
     let intent = async (req, res) => {
         const userid = req.body.userid;
         const price = req.body.price || 500;
@@ -94,9 +101,76 @@ DB.getDB.then((DB) => {
     };
 
 
+    /**
+ * @swagger
+ * /payments/create-payment-intent:
+ *   post:
+ *     summary: Creates a Stripe Payment Intent
+ *     tags: [Payments]
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             properties:
+ *               userid:
+ *                 type: string
+ *               price:
+ *                 type: number
+ *               description:
+ *                 type: string
+ *     responses:
+ *       200:
+ *         description: OK
+ */
     router.post("/create-payment-intent", intent);
+    /**
+ * @swagger
+ * /payments/intent:
+ *   post:
+ *     summary: Creates a Stripe Payment Intent (Alias for /create-payment-intent)
+ *     tags: [Payments]
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             properties:
+ *               userid:
+ *                 type: string
+ *               price:
+ *                 type: number
+ *               description:
+ *                 type: string
+ *     responses:
+ *       200:
+ *         description: OK
+ */
     router.post("/intent", intent);
 
+    /**
+ * @swagger
+ * /payments/register:
+ *   post:
+ *     summary: Registers a payment after a successful Stripe transaction
+ *     tags: [Payments]
+ *     requestBody:
+ *       required: true
+ *       content:
+ *         application/json:
+ *           schema:
+ *             type: object
+ *             properties:
+ *               userid:
+ *                 type: string
+ *               result:
+ *                 type: object
+ *     responses:
+ *       200:
+ *         description: OK
+ */
     router.post("/register", async (req, res) => {
         const userid = req.body.userid;
         const result = req.body.result;