[mirotalksfu] - improve primary button UI

public/css/landing.css

@@ -1080,8 +1080,11 @@ label {
 }
 .button-primary:hover {
     background: #0982f4;
-    background: linear-gradient(65deg, #0275e1 0, #198ffd 100%);
+    background: linear-gradient(65deg, #0275e1 0%, #198ffd 100%);
     border-radius: 6px;
+    filter: brightness(1.1) saturate(1.2);
+    transform: scale(1.05);
+    box-shadow: 0 6px 20px rgba(0, 123, 255, 0.4);
 }
 .button-block {
     display: flex;