Compress what the browser downloads, and stop one tile taking the page

**nginx served the bundle uncompressed and uncacheable.** The base image
ships gzip commented out and nothing set `Cache-Control`, so every load
carried the whole thing and every reload cost a 304 per asset. Measured on
the built image: the entry chunk 838 kB → 311 kB, the Monaco chunk 2.66 MB
→ 832 kB, and the ~50 content-hashed assets are now immutable for a year.
`index.html` is explicitly `no-cache`, since it is what names the rest.

**A widget that throws no longer blanks the screen.** There was one error
boundary in the app, on the root route, so anything that threw replaced
everything including the navigation — on `/view/{name}`, an unattended wall
panel with no way back. Each tile has its own boundary now, and the app
shell has one inside it so a screen that fails leaves the sidebar standing.
`react-error-boundary` was already a dependency and imported nowhere.

**`localStorage` cannot take the app down.** Reaching it raises where the
browser blocks site data, and `setItem` raises once the origin's quota is
full — which the flow editor's node clipboard, carrying whole Python
sources, can genuinely reach. Thrown from a key handler that escaped to
`window.onerror`, which the single root boundary then turned into a blank
page. `lib/safeStorage.ts` is the guarded pair the pre-paint theme script in
`index.html` was already using; a copy too large to store now says so.

Queries default to `staleTime: 5000` — below every poll interval on any
screen, so nothing polls less often than it did, but a route mounting twice
in a few seconds stops refetching everything it touches. Window-focus
refetching is off: the socket pushes what changes and a reconnect
invalidates what it feeds, so a focus event has nothing of its own to say.
Home alone reads about ten queries on every one of those.

Render cost, two that showed up in the audit:

- `LogsPanel` was rendered unconditionally by the dock and decided inside
  itself whether to draw, so with the panel *shut* it still subscribed to
  the log store and re-filtered five hundred lines per line a flow
  published. It returns before any of that now.
- `HealthActivity` subscribed to the whole engine-event array and used one
  number from it, so a flapping node re-rendered the component that draws
  Home's two uPlot charts — each of which rebuilds its series on every
  render by design. It subscribes to that number.
- the global search bucketed the index nine times per keystroke, once per
  group. One pass, and each group offers at most twenty.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01M6hPWS6YEbT1P8LxhhFb2T

frontend/src/routes/_layout.tsx

@@ -1,6 +1,7 @@
 import { createFileRoute, Outlet, redirect } from "@tanstack/react-router"
 
 import { ConnectionNotice } from "@/components/Common/ConnectionNotice"
+import ErrorComponent from "@/components/Common/ErrorComponent"
 import { Footer } from "@/components/Common/Footer"
 import { useFlowSocket } from "@/components/Flow/useFlowSocket"
 import AppSidebar from "@/components/Sidebar/AppSidebar"
@@ -13,6 +14,10 @@ import { isLoggedIn } from "@/hooks/useAuth"
 
 export const Route = createFileRoute("/_layout")({
   component: Layout,
+  // Inside the shell rather than at the root, so a screen that throws leaves
+  // the sidebar standing and somebody can navigate away from it. The root's
+  // own boundary replaces the whole app, navigation included.
+  errorComponent: () => <ErrorComponent />,
   beforeLoad: async () => {
     if (!isLoggedIn()) {
       throw redirect({