local activity storage and convert page fixes

- Replace rdp dependency with inline pure-Python RDP implementation
    so the bincio wheel runs in Pyodide (no pure-Python wheel existed for rdp)
  - Fix convert page script: remove define:vars so Vite bundles it and
    TypeScript imports (localstore, format) work correctly
  - Rename wheel to proper PEP 427 filename (bincio-0.1.0-py3-none-any.whl)
  - Use en-GB date format on convert result, consistent with the feed
  - Add /activity/local/ page + LocalActivityDetail for IDB-only activities;
    feed links local activities there instead of the SSG route
  - Fix getStaticPaths: try public/data symlink as fallback, never crash on
    missing index.json
  - Fix ActivityDetail.onMount: load detail even when detail_url is absent
    so locally converted activities show map and charts
  - Derive track_url and detail_url from id in toSummary() since they are
    not present in the detail JSON
  - Reload on bfcache restore (pageshow) so client:only components re-mount
    after back navigation

site/src/lib/localstore.ts

@@ -65,6 +65,12 @@ export async function listLocalActivities(): Promise<ActivitySummary[]> {
   return (await idbGet<ActivitySummary[]>('/data/local-index')) ?? [];
 }
 
+/** Return the summary for a single locally-stored activity, or null. */
+export async function getLocalActivity(id: string): Promise<ActivitySummary | null> {
+  const list = await listLocalActivities();
+  return list.find(a => a.id === id) ?? null;
+}
+
 /** Return true if at least one activity is stored locally. */
 export async function hasLocalActivities(): Promise<boolean> {
   const list = await listLocalActivities();
@@ -83,7 +89,12 @@ const SUMMARY_KEYS = [
 ] as const;
 
 function toSummary(detail: Record<string, unknown>): ActivitySummary {
-  return Object.fromEntries(
+  const id = detail.id as string;
+  const summary = Object.fromEntries(
     SUMMARY_KEYS.filter(k => k in detail).map(k => [k, detail[k]])
   );
+  // These live in the index summary, not the detail JSON — derive from id
+  if (!summary.detail_url) summary.detail_url = `activities/${id}.json`;
+  if (!summary.track_url && detail.bbox)  summary.track_url = `activities/${id}.geojson`;
+  return summary;
 }