Expand the timeline to 100% height in panel mode.

src/scss/thumbnail-feature-event.scss

@@ -12,6 +12,10 @@ ha-icon {
   // Safari will occasionally not load thumbnails correctly with display block.
   display: inline-block;
 
+  // Ensure no whitespace around img with inline-block display.
+  vertical-align: top;
+  margin: 0;
+
   border-radius: var(--frigate-card-css-border-radius, var(--ha-card-border-radius, 4px));
 
   max-width: var(--frigate-card-thumbnail-size);