Added UserModel, Added Login and Logout and authorization, Made dark mode default

src/Views/Home/AccessDenied.cshtml

@@ -0,0 +1,9 @@
+@{
+    ViewData["Title"] = "Access denied";
+}
+
+<div class="text-center">
+    <h1 class="display-4">Access denied</h1>
+    <p>You currently do not have permission to access the page you tried to access.</p>
+    <a href="/Home/Login">Please click here to return to the login page</a>
+</div>

src/Views/Home/Login.cshtml

@@ -0,0 +1,28 @@
+@{
+    ViewData["Title"] = "Login";
+}
+
+<div class="text-center">
+    <h1 class="display-4">Login</h1>
+    @{
+        if (Model.ErrorText is not null)
+        {
+            <div class="alert alert-danger text-center login-error">
+                <h2>@Model.ErrorText</h2>
+            </div>
+        }
+    }
+    <form method="post" action="/Home/Login" class="mt-4" style="max-width: 400px; margin: auto;">
+        <div class="form-group mb-3">
+            <label for="username" class="form-label">Username</label>
+            <input type="text" class="form-control" id="username" name="username" required>
+        </div>
+
+        <div class="form-group mb-3">
+            <label for="password" class="form-label">Password</label>
+            <input type="password" class="form-control" id="password" name="password" required>
+        </div>
+
+        <button type="submit" class="btn btn-primary w-100">Login</button>
+    </form>
+</div>