Fix export chevron: wider padding + stop click propagation

The chevron was too narrow (px-1.5 → px-2.5) and clicks were
caught by the outside-click handler before toggling the dropdown.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/planner/app/components/ExportButton.tsx

@@ -83,8 +83,8 @@ export function ExportButton({ yjs }: { yjs: YjsState }) {
           {t("exportGpx")}
         </button>
         <button
-          onClick={() => setOpen((v) => !v)}
-          className="rounded-r border-l border-gray-300 bg-gray-100 px-1.5 py-1 text-sm text-gray-700 hover:bg-gray-200"
+          onClick={(e) => { e.stopPropagation(); setOpen((v) => !v); }}
+          className="rounded-r border-l border-gray-300 bg-gray-100 px-2.5 py-1 text-sm text-gray-700 hover:bg-gray-200"
         >
           ▾
         </button>