Add first clip button and update region names in video player

templates/index.html

@@ -31,8 +31,15 @@
     <div class="layout">
       <!-- Region filter bar -->
       <nav class="region-bar" id="regionBar">
-        <span class="region-label">Region:</span>
-        <button class="region-btn active" data-region="">All</button>
+        <span class="region-label">Shortcuts:</span>
+        <button
+          class="region-btn"
+          id="firstBtn"
+          title="First clip"
+          aria-label="First clip"
+        >
+          Start
+        </button>
       </nav>
 
       <!-- Video Player -->