Implement server-side authentication and update login UI texts

public/app.js

@@ -29,15 +29,27 @@ document.addEventListener('DOMContentLoaded', function() {
         const username = document.getElementById('username').value;
         const password = document.getElementById('password').value;
 
-        // Simple authentication check (replace with your own logic)
-        if (username === 'fredrik' && password === 'apa') {
-            sessionStorage.setItem('loggedIn', 'true');
-            loginContainer.style.display = 'none';
-            appContainer.style.display = 'block';
-            loadTags();
-        } else {
-            loginMessage.textContent = 'Invalid username or password';
-        }
+        // Send credentials to the server for validation
+        fetch('/login', {
+            method: 'POST',
+            headers: {
+                'Content-Type': 'application/json',
+                'Authorization': 'Basic ' + btoa(username + ':' + password)
+            }
+        })
+        .then(response => {
+            if (response.ok) {
+                sessionStorage.setItem('loggedIn', 'true');
+                loginContainer.style.display = 'none';
+                appContainer.style.display = 'block';
+                loadTags();
+            } else {
+                loginMessage.textContent = 'Invalid username or password';
+            }
+        })
+        .catch(error => {
+            loginMessage.textContent = 'Error logging in';
+        });
     });
 
     document.getElementById('taskForm').addEventListener('submit', function(e) {