feat(settings): move Hide IP toggle into Settings modal, persist it

Hide-IP was a sidebar button held only in memory, so it reset on reload.
Moved it into the Settings modal Canvas section and persist it to
localStorage (new ipDisplay util); the canvas store now seeds hideIp from
storage and writes through on toggleHideIp/setHideIp. Settings is now also
reachable in standalone (no-backend) builds, with the backend-only status
interval guarded so the modal still works there.

ha-relevant: yes

frontend/src/utils/__tests__/ipDisplay.test.ts

@@ -0,0 +1,22 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import { readHideIp, writeHideIp } from '@/utils/ipDisplay'
+
+describe('ipDisplay persistence', () => {
+  beforeEach(() => localStorage.clear())
+
+  it('defaults to false when nothing is stored', () => {
+    expect(readHideIp()).toBe(false)
+  })
+
+  it('round-trips true', () => {
+    writeHideIp(true)
+    expect(localStorage.getItem('homelable.hideIp')).toBe('true')
+    expect(readHideIp()).toBe(true)
+  })
+
+  it('round-trips false', () => {
+    writeHideIp(true)
+    writeHideIp(false)
+    expect(readHideIp()).toBe(false)
+  })
+})

frontend/src/utils/ipDisplay.ts

@@ -0,0 +1,21 @@
+// Persisted client-side preference for masking IP addresses on the canvas.
+// Kept in localStorage (per-user UI preference, not canvas data) so it
+// survives a page reload.
+
+const KEY = 'homelable.hideIp'
+
+export function readHideIp(): boolean {
+  try {
+    return localStorage.getItem(KEY) === 'true'
+  } catch {
+    return false
+  }
+}
+
+export function writeHideIp(value: boolean): void {
+  try {
+    localStorage.setItem(KEY, String(value))
+  } catch {
+    /* quota / SSR */
+  }
+}