Fix thead/tbody alignment by adding matching border to header

The tbody first column had a 6px left border for priority indicator,
but the thead first column didn't have this border, causing misalignment.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

assets/css/dashboard.css

@@ -1486,6 +1486,11 @@ tbody tr.keyboard-selected td {
     text-shadow: 0 0 5px rgba(0, 255, 65, 0.5);
 }
 
+/* Priority indicator border - match header and body first column */
+thead tr th:first-child {
+    border-left: 6px solid var(--terminal-green);
+}
+
 tbody tr td:first-child {
     border-left: 6px solid;
 }