ui: fix undefined location filter variable on the Machines page

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

cmd/rollcall/web/app.js

@@ -172,6 +172,7 @@ function stateCell(m) {
 }
 function pageMachines() {
   const r = route(); if (r.arg && !S.states.size) S.states.add(r.arg);
+  const L = S.loc;
   const ms = filtered();
   const by = {}; for (const m of S.machines) by[m.state] = (by[m.state] || 0) + 1;
   const tagCount = {}; for (const m of S.machines) for (const t of m.tags || []) tagCount[t] = (tagCount[t] || 0) + 1;