fix: audit log pagination + full-width table, board card button alignment, light sidebar dither

- Audit log: backend only returns a next cursor when the page is full, so the
  "Load more" button no longer needs two clicks (and hides at the last page).
  Table now spans the full screen width and long detail JSON wraps instead of
  overflowing.
- Bounty board: pin each card's action row to the bottom so "Request
  assignment" lines up across equal-height cards.
- Light theme: restore the Y2K dither texture on the sidebar nav panel.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

web/static/js/admin.js

@@ -362,6 +362,7 @@ async function loadAudit(reset = true) {
   try {
     const entity = encodeURIComponent(document.getElementById('audit-entity').value.trim());
     if (reset) auditCursor = '';
+    else if (!auditCursor) return; // already at the last page
     const res = await api('GET', `/api/v1/admin/audit-log?entityId=${entity}&cursor=${auditCursor}`);
     auditCursor = res.nextCursor;
     const rows = res.entries.map((e) => {
@@ -380,6 +381,7 @@ async function loadAudit(reset = true) {
     const tbody = document.querySelector('#audit-table tbody');
     if (reset) tbody.replaceChildren(...rows);
     else tbody.append(...rows);
+    document.getElementById('audit-more').hidden = !auditCursor;
   } catch (e) { showErr(e); }
 }
 document.getElementById('audit-apply').addEventListener('click', () => loadAudit(true));