feat: auth system - login/logout/session with rate limiting

edu/js/auth.js

@@ -0,0 +1,22 @@
+'use strict';
+
+var Auth = {
+    handleLogin: function(e) {
+        e.preventDefault();
+        var user = document.getElementById('login-user').value.trim();
+        var pass = document.getElementById('login-pass').value;
+        var errorEl = document.getElementById('login-error');
+        errorEl.style.display = 'none';
+
+        API.post('/login', { username: user, password: pass })
+            .then(function(data) { App.setUser(data.user); })
+            .catch(function(err) {
+                errorEl.textContent = err.message || 'Anmeldung fehlgeschlagen';
+                errorEl.style.display = 'block';
+            });
+    },
+
+    handleLogout: function() {
+        API.post('/logout').catch(function() {}).then(function() { App.showLogin(); });
+    }
+};