First skeleton of scan mode.

src/scss/card.scss

@@ -33,11 +33,29 @@
   align-items: center;
   justify-content: center;
 
+  // Include the borders in the sizing (to keep the triggered warning pulse
+  // visible in fullscreen).
+  box-sizing: border-box;
+
   // Hide scrollbar: Firefox
   scrollbar-width: none;
   // Hide scrollbar: IE and Edge
   -ms-overflow-style: none;
 }
+.frigate-card-contents.triggered {
+  @keyframes warning-pulse {
+    0% {
+      border: solid 1px rgba(0,0,0,0);
+    }
+    50% {
+      border: solid 1px var(--warning-color);
+    }
+    100% {
+      border: solid 1px rgba(0,0,0,0);
+    }
+  }
+  animation: warning-pulse 5s infinite;  
+}
 
 /* Hide scrollbar for Chrome, Safari and Opera */
 .frigate-card-contents::-webkit-scrollbar {