feat(web): click Executions' Started time to toggle relative/absolute

Both renderings are pre-rendered server-side into a <button>'s
data-relative/data-absolute attributes; app.js swaps textContent (and the
hover title, to the opposite value) on click, delegated on document.body
so it survives the card's own 5s htmx poll without needing to re-wire
after every swap. Click again to swap back.

src/ci_orchestrator/web/static/app.js

@@ -204,6 +204,22 @@
     }
   });
 
+  // Executions "Started" cell: click swaps between the relative and
+  // absolute time already rendered into the button's own data attributes --
+  // no request. Delegated on body (not the button itself) so it keeps
+  // working after the Executions card's own 5s htmx poll replaces the row.
+  document.body.addEventListener("click", function (evt) {
+    var btn = evt.target.closest(".time-toggle");
+    if (!btn) {
+      return;
+    }
+    var next = btn.dataset.showing === "relative" ? "absolute" : "relative";
+    var shown = next === "relative" ? "absolute" : "relative";
+    btn.textContent = btn.dataset[next];
+    btn.title = btn.dataset[shown];
+    btn.dataset.showing = next;
+  });
+
   document.addEventListener("DOMContentLoaded", function () {
     observeStack();
     processSlot(document.getElementById("action-slot"));