fix: resolve final TypeScript compilation errors and add documentation

Author: Brijesh Kumar Joshi

server/src/routes/auth.ts

@@ -81,19 +81,15 @@ router.post('/register', asyncHandler(async (req: Request, res: Response) => {
   });
 
   // Generate JWT token
-  const token = jwt.sign(
-    { userId: user.id },
-    config.JWT_SECRET,
-    { expiresIn: config.JWT_EXPIRES_IN }
-  );
+  const token = signJWT({ userId: user.id });
 
   logger.info(`New user registered: ${user.username} (${user.email})`);
 
   res.status(201).json({
     success: true,
     data: {
       user,
-      token: signJWT({ userId: user.id })
+      token
     }
   });
 }));
@@ -137,11 +133,7 @@ router.post('/login', asyncHandler(async (req: Request, res: Response) => {
   }
 
   // Generate JWT token
-  const token = jwt.sign(
-    { userId: user.id },
-    config.JWT_SECRET,
-    { expiresIn: config.JWT_EXPIRES_IN }
-  );
+  const token = signJWT({ userId: user.id });
 
   logger.info(`User logged in: ${user.username} (${user.email})`);
 
@@ -155,7 +147,7 @@ router.post('/login', asyncHandler(async (req: Request, res: Response) => {
         avatar: user.avatar,
         createdAt: user.createdAt
       },
-      token: signJWT({ userId: user.id })
+      token
     }
   });
 }));