Add live/paused toggle, env badge, remove topnav search, rename labels

- Add LIVE/PAUSED toggle button that auto-refreshes search results every 5s
- Source environment badge from VITE_ENV_NAME env var (defaults to DEV locally, PRODUCTION in Docker)
- Remove search trigger button from topnav (command palette still available via keyboard)
- Rename "Transaction Explorer" to "Route Explorer" and "Active Now" to "In-Flight"

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

ui/src/components/layout/TopNav.module.css

@@ -61,43 +61,6 @@
   gap: 16px;
 }
 
-.searchTrigger {
-  display: flex;
-  align-items: center;
-  gap: 8px;
-  padding: 5px 12px 5px 10px;
-  background: var(--bg-raised);
-  border: 1px solid var(--border);
-  border-radius: var(--radius-sm);
-  color: var(--text-muted);
-  font-size: 13px;
-  font-family: var(--font-body);
-  cursor: pointer;
-  transition: border-color 0.15s, color 0.15s;
-}
-
-.searchTrigger:hover {
-  border-color: var(--text-muted);
-  color: var(--text-secondary);
-}
-
-.searchTrigger svg {
-  width: 14px;
-  height: 14px;
-  opacity: 0.5;
-}
-
-.kbdKey {
-  font-family: var(--font-mono);
-  font-size: 11px;
-  padding: 1px 5px;
-  background: var(--bg-hover);
-  border: 1px solid var(--border);
-  border-radius: 4px;
-  color: var(--text-muted);
-  line-height: 1.4;
-}
-
 .envBadge {
   font-family: var(--font-mono);
   font-size: 11px;