feat: revise login screen with logo and smooth transition to splash

- Replace 'Login to Emby' heading with sofarr logo and subtitle
- Subtitle reads 'Login with your Emby credentials'
- Login form fades out smoothly before splash screen appears
- Form labels remain left-aligned within centered login box

public/style.css

@@ -545,6 +545,12 @@ body {
   align-items: center;
   min-height: 100vh;
   padding: 20px;
+  opacity: 1;
+  transition: opacity 0.3s ease-out;
+}
+
+.login-container.fade-out {
+  opacity: 0;
 }
 
 .login-box {
@@ -555,17 +561,24 @@ body {
   width: 100%;
   max-width: 380px;
   transition: background 0.3s;
+  text-align: center;
 }
 
-.login-box h2 {
-  color: var(--text-primary);
+.login-logo {
+  max-width: 180px;
+  width: 60%;
+  margin-bottom: 12px;
+}
+
+.login-subtitle {
+  color: var(--text-secondary);
   margin-bottom: 24px;
-  text-align: center;
-  font-size: 1.5rem;
+  font-size: 0.85rem;
 }
 
 .form-group {
   margin-bottom: 16px;
+  text-align: left;
 }
 
 .form-group label {