feat: redesign Deployments tab with Overview + Configuration sub-tabs

Overview sub-tab:
- Deployments table with env badge, version, status, URL, deployed time
- Actions (Start/Stop) scoped to selected environment; other envs show
  "switch env to manage" hint with muted rows
- Versions list with per-env deploy target picker

Configuration sub-tab:
- Read-only by default with Edit mode gate (Cancel/Save banner)
- Agent observability: engine level, payload capture with size unit
  selector, log levels, metrics toggle, sampling, replay and route
  control (default enabled)
- Container resources: memory/CPU limits, exposed ports as deletable
  pills with inline add input
- Environment variables: key-value editor with add/remove
- Reuses existing ApplicationConfig API for agent config push via SSE

Tab renamed from "Apps" to "Deployments" in the tab bar.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/ContentTabs.tsx

@@ -23,7 +23,7 @@ export function ContentTabs({ active, onChange, scope }: ContentTabsProps) {
   const canControl = useCanControl();
   const tabs = useMemo(() => {
     if (!canControl) return BASE_TABS;
-    return [...BASE_TABS, { label: 'Apps', value: 'apps' }];
+    return [...BASE_TABS, { label: 'Deployments', value: 'apps' }];
   }, [canControl]);
 
   return (