Add authentication support with login/logout UI

- Introduced AuthService, IAuthApiClient, and AuthApiClient for managing authentication state and API calls (login, logout, session restore).
- Added Login.razor and LoginLayout.razor for the login page, including styling and logic.
- MainLayout.razor now checks authentication on load, restores sessions from sessionStorage, and redirects to /login if unauthenticated. Displays username and logout button when logged in.
- Implemented JS interop (authStorage) for persisting authentication info in sessionStorage.
- Registered AuthService, CookieContainer, and API clients in Program.cs to share cookies and support authentication.
- Updated AppSettings and appsettings files to support separate ApiBaseUrl and DataApiBaseUrl.
- Minor CSS improvements for username display in the top bar.

DbFirst.BlazorWebApp/Components/Pages/Login.razor.css

@@ -0,0 +1,111 @@
+.login-container {
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    min-height: calc(100vh - 2rem);
+}
+
+.login-card {
+    width: 100%;
+    max-width: 400px;
+    padding: 2rem;
+    border-radius: 8px;
+    border: 1px solid var(--band-editor-border, #dee2e6);
+    background-color: var(--band-editor-bg, #fff);
+    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.08);
+}
+
+.login-header {
+    text-align: center;
+    margin-bottom: 1.75rem;
+}
+
+.login-brand {
+    font-size: 1.8rem;
+    font-weight: 700;
+    color: #1b6ec2;
+    letter-spacing: 0.02em;
+}
+
+.login-subtitle {
+    margin-top: 0.35rem;
+    margin-bottom: 0;
+    font-size: 0.9rem;
+    color: #6c757d;
+}
+
+.login-field {
+    margin-bottom: 1rem;
+}
+
+.login-label {
+    display: block;
+    font-size: 0.85rem;
+    font-weight: 500;
+    margin-bottom: 0.3rem;
+}
+
+.login-actions {
+    margin-top: 1.25rem;
+}
+
+/* Gemeinsamer Stil für Text- und Passwort-Eingabefelder */
+.login-text-input {
+    display: block;
+    width: 100%;
+    height: 2.25rem;
+    padding: 0.25rem 0.65rem;
+    font-size: 1rem;
+    font-family: inherit;
+    line-height: 1.5;
+    color: inherit;
+    background-color: transparent;
+    border: 1px solid #ced4da;
+    border-radius: 4px;
+    box-sizing: border-box;
+    outline: none;
+    transition: border-color 0.15s ease-in-out, box-shadow 0.15s ease-in-out;
+}
+
+    .login-text-input:focus {
+        border-color: #86b7fe;
+        box-shadow: 0 0 0 0.2rem rgba(13, 110, 253, 0.25);
+    }
+
+/* Submit-Button */
+.login-submit-btn {
+    display: block;
+    width: 100%;
+    padding: 0.45rem 1rem;
+    font-size: 1rem;
+    font-family: inherit;
+    font-weight: 500;
+    color: #fff;
+    background-color: #1b6ec2;
+    border: 1px solid #1861ac;
+    border-radius: 4px;
+    cursor: pointer;
+    transition: background-color 0.15s ease-in-out, border-color 0.15s ease-in-out;
+}
+
+    .login-submit-btn:hover:not(:disabled) {
+        background-color: #1558a0;
+        border-color: #1456a0;
+    }
+
+    .login-submit-btn:disabled {
+        opacity: 0.65;
+        cursor: not-allowed;
+    }
+
+/* Dark-Mode */
+.app-dark .login-text-input {
+    border-color: #555;
+    color: #e8e8e8;
+    background-color: #2d2d2d;
+}
+
+    .app-dark .login-text-input:focus {
+        border-color: #6cb6ff;
+        box-shadow: 0 0 0 0.2rem rgba(108, 182, 255, 0.25);
+    }