Cleanup: fix eslint warnings, button loading state, inspector footer hint

- app.js: replace != with !== (eqeqeq rule) on resolved_24h null check
  and totalActive pagination check
- style.css: extend loading state to all .lt-btn.is-loading (not just
  refresh button), so suppressions form submit shows disabled feedback;
  remove dead .link-collapse-bar rule
- base.html: add inspector page to footer R=REFRESH hint; update
  keyboard shortcut table to include Inspector in refresh shortcut doc

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/app.js

@@ -95,7 +95,7 @@ function updateStatusBar(summary, lastCheck, daemonOk) {
   const scRes  = document.getElementById('stat-resolved-val');
   if (scCrit) scCrit.textContent = critCount;
   if (scWarn) scWarn.textContent = warnCount;
-  if (scRes && summary.resolved_24h != null) scRes.textContent = summary.resolved_24h;
+  if (scRes && summary.resolved_24h !== null && summary.resolved_24h !== undefined) scRes.textContent = summary.resolved_24h;
   const statCritCard = document.getElementById('stat-critical');
   if (statCritCard) statCritCard.classList.toggle('lt-stat-card--alert', critCount > 0);
 
@@ -207,7 +207,7 @@ function updateEventsTable(events, totalActive) {
     return;
   }
 
-  const truncated = totalActive != null && totalActive > active.length;
+  const truncated = totalActive !== null && totalActive !== undefined && totalActive > active.length;
   const countNotice = truncated
     ? `<div class="pagination-notice">Showing ${active.length} of ${totalActive} active alerts &mdash; <a href="/api/events?limit=1000">view all via API</a></div>`
     : '';