EventGantt: suppress click-on-bar that fires right after drag

Without this, dragging a bar fired mouseup → onClick in the same tick,
opening the edit popover with stale (pre-mutation) year values. The
PATCH succeeded but the popover showed the old year_start until React
Query refetched. Adding a 250ms debounce after drag-end before
re-enabling click-to-edit.

Tests + build green.

frontend/src/components/EventGantt.tsx

@@ -151,6 +151,11 @@ function Inner({
   // Pixel-level offset applied during drag (without committing).
   const [dragOffset, setDragOffset] = useState<{ id: number; dx: number; mode: DragMode } | null>(null);
   const [popover, setPopover] = useState<PopoverState | null>(null);
+  // Timestamp of the most recent drag-end. We use it to suppress the
+  // synchronous `onClick` that fires on `mouseup` after a successful
+  // drag — that click would otherwise open the edit popover with stale
+  // (pre-drag) field values, since React Query hasn't re-fetched yet.
+  const lastDragEnd = useRef<number>(0);
 
   useEffect(() => {
     const onMove = (e: MouseEvent) => {
@@ -169,6 +174,7 @@ function Inner({
       drag.current = null;
       setDragOffset(null);
       if (Math.abs(dyears) < 1) return;  // sub-year drag = ignore
+      lastDragEnd.current = performance.now();
       let body: LifeEventPatchBody = {};
       if (mode === 'move') {
         const newStart = clamp(origYearStart + dyears, 0, horizonYears - 1);
@@ -224,6 +230,9 @@ function Inner({
 
   const onBarClick = (e: React.MouseEvent, ev: LifeEvent) => {
     e.stopPropagation();
+    // Suppress the click that fires immediately after a drag — the
+    // popover would otherwise open with stale (pre-mutation) values.
+    if (performance.now() - lastDragEnd.current < 250) return;
     const point = localPoint(e);
     if (!point) return;
     setPopover({ kind: 'edit', x: point.x, y: point.y, event: ev });