fix: resolve widget overlaps after resize

When resizing a widget, any widget that gets overlapped is automatically
pushed down to clear the collision. Multi-pass overlap detection ensures
cascading widgets are all resolved. Positions persisted to API.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/app/dashboards/[id]/page.tsx

@@ -194,9 +194,49 @@ export default function DashboardPage({ params }: { params: Promise<{ id: string
       document.removeEventListener("mousemove", onMove);
       document.removeEventListener("mouseup", onUp);
       setResizingId(null);
-      const updated = widgets.find((w) => w.id === widgetId);
+
-      if (updated) {
+      // Resolve overlaps: push overlapping widgets out of the way
-        await updateWidget(id, widgetId, { position: updated.position });
+      let resolved = widgets.map((w) => (w.id === widgetId ? { ...w, position: { ...w.position } } : w));
+      const movedIds = new Set<string>();
+
+      // Keep pushing until no overlaps
+      for (let pass = 0; pass < 10; pass++) {
+        let hasOverlap = false;
+        for (let i = 0; i < resolved.length; i++) {
+          for (let j = i + 1; j < resolved.length; j++) {
+            const a = resolved[i].position;
+            const b = resolved[j].position;
+            const ax2 = a.x + a.w;
+            const ay2 = a.y + a.h;
+            const bx2 = b.x + b.w;
+            const by2 = b.y + b.h;
+
+            if (ax2 > b.x && a.x < bx2 && ay2 > b.y && a.y < by2) {
+              hasOverlap = true;
+              // Fix the resized widget in place, push the OTHER widget down
+              const toMove = widgetId === resolved[i].id ? j : i;
+              const movedW = resolved[toMove];
+              const fixedW = resolved[widgetId === resolved[i].id ? i : j];
+              const newY = fixedW.position.y + fixedW.position.h;
+              resolved[toMove] = {
+                ...movedW,
+                position: { ...movedW.position, y: newY },
+              };
+              movedIds.add(movedW.id);
+            }
+          }
+        }
+        if (!hasOverlap) break;
+      }
+
+      setWidgets(resolved);
+
+      // Persist positions
+      for (const w of resolved) {
+        const original = widgets.find((o) => o.id === w.id);
+        if (original && (original.position.y !== w.position.y || original.position.h !== w.position.h)) {
+          await updateWidget(id, w.id, { position: w.position });
+        }
       }
     };