Feed: fix date range eager-load — use primary let-vars, cover feed pages

Previous attempt used dateFrom (a derived $: variable) as the trigger which
Svelte 5 doesn't reliably track as a dependency of a side-effect $: block.
Replace with the primary let-variables (customFrom, customTo, datePre) that
Svelte does track statically.

Also extend eager-loading to cover the global combined feed (feedNextPage)
so date/search filtering works on multi-user instances too, not just per-user
profile pages (pendingShards).

site/src/components/ActivityFeed.svelte

@@ -134,8 +134,12 @@
 
   // When a search query or any date filter is active, eagerly load all
   // remaining shards so results aren't limited to the initially-loaded year.
+  // Use only primary let-variables here — Svelte 5 doesn't reliably track
+  // derived $: variables as dependencies of side-effect $: blocks.
   let loadingAllShards = false;
-  $: if ((query.trim() || dateFrom) && pendingShards.length > 0 && !loadingAllShards) {
+  let loadingAllFeedPages = false;
+
+  $: if ((query.trim() || customFrom || customTo || datePre !== 'all') && pendingShards.length > 0 && !loadingAllShards) {
     loadingAllShards = true;
     (async () => {
       while (pendingShards.length > 0) {
@@ -154,6 +158,25 @@
     })();
   }
 
+  $: if ((query.trim() || customFrom || customTo || datePre !== 'all') && feedNextPage > 0 && !loadingAllFeedPages) {
+    loadingAllFeedPages = true;
+    (async () => {
+      while (feedNextPage > 0) {
+        const page = feedNextPage;
+        feedNextPage = page < feedTotalPages ? page + 1 : 0;
+        try {
+          const fresh = await loadCombinedFeedPage(base, page);
+          const existing = new Map(all.map(a => [a.id, a]));
+          for (const a of fresh) if (!existing.has(a.id)) existing.set(a.id, a);
+          all = [...existing.values()].sort((a, b) =>
+            (b.started_at ?? '').localeCompare(a.started_at ?? ''),
+          );
+        } catch { /* ignore — partial results still useful */ }
+      }
+      loadingAllFeedPages = false;
+    })();
+  }
+
   $: if (mounted) {
     const params = new URLSearchParams(window.location.search);
     if (sport === 'all') params.delete('sport'); else params.set('sport', sport);