feat(theming): wire the three navs and add the admin nav builder

Phases 6-8 of docs/website/THEMING_AND_NAV.md. The public header, the admin
sidebar and the player portal now read their override row, and /admin/navigation
writes them: rename, reorder by drag, hide, and — on the admin sidebar — move a
row into another existing section.

The merge always runs BEFORE the role and shard-feature filters in the layouts,
which are unchanged and remain the boundary. An override is presentation: it
cannot introduce a route, cannot touch a `roles` or `feature` gate, and a stored
`hidden: false` on a gated item shows nobody anything.

The design scoped these phases as client work, but the server had no way to
store a nav row: updateSettings validates and stringifies theme_visual and
brand_assets and lets everything else through, so a nav object would have been
written as "[object Object]" and read as absent for ever. utils/navOverrides.js
mirrors utils/brandAssets.js — strict on write with the offending key named,
forgiving on read. It validates shape only; whether a `to` exists is settled
client-side at merge time, because the base NAV arrays are client constants and
a server-side copy would be a second source of truth that drifts.

The nav editor cannot be hidden — its own toggle is disabled, the write path
drops `hidden` on that one `to`, and AdminLayout strips it again before merging,
which also covers a row edited straight in the database.

Orders are written only when the sequence actually differs from the code's, and
the comparison is restricted to the rows the editing admin can see, so renaming
one item does not pin the position of every other one and a role- or
feature-gated item missing from their palette is not mistaken for a reorder.

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

client/src/routes/player/PlayerPortalLayout.jsx

@@ -1,8 +1,11 @@
+import { useMemo } from 'react'
 import { NavLink, Outlet, useNavigate, useLocation } from 'react-router-dom'
 import MoonDot from '../../components/MoonDot.jsx'
 import BrandLogo from '../../components/BrandLogo.jsx'
 import { useAuth } from '../../contexts/AuthContext.jsx'
 import { useSite } from '../../contexts/SiteContext.jsx'
+import { applyNavOverrides } from '../../lib/navOverrides.js'
+import { useNavOverrides } from '../../lib/useNavOverrides.js'
 
 // Shared shell for the logged-in player portal. Uses the same sidebar shell as
 // Admin (icon nav, sticky content header, footer sign-out) so the two logged-in
@@ -31,7 +34,11 @@ const IconUser = () => <Icon><circle cx="12" cy="8" r="4" /><path d="M4 21a8 8 0
 const IconGear = () => <Icon><circle cx="12" cy="12" r="3" /><path d="M12 2v3M12 19v3M2 12h3M19 12h3M4.9 4.9l2.1 2.1M17 17l2.1 2.1M19.1 4.9L17 7M7 17l-2.1 2.1" /></Icon>
 const IconShield = () => <Icon><path d="M12 3l7 3v5c0 5-3.5 8-7 10-3.5-2-7-5-7-10V6z" /><path d="M9 12l2 2 4-4" /></Icon>
 
-const NAV = [
+// Exported because Admin -> Navigation edits this list. It stays declared here;
+// the editor may only relabel, reorder and hide what it finds (§7). No row
+// carries a gate — every player sees all three — so the merged result is what
+// renders, with no filter after it.
+export const NAV = [
   { to: '/player', label: 'Characters', end: true, icon: IconUser },
   { to: '/account/appeals', label: 'Appeals', icon: IconShield },
   { to: '/account', label: 'Account', end: true, icon: IconGear },
@@ -61,6 +68,8 @@ const navBtnBase = {
 export default function PlayerPortalLayout() {
   const { user, logout } = useAuth()
   const { siteTitle } = useSite()
+  const navOverrides = useNavOverrides()
+  const nav = useMemo(() => applyNavOverrides(NAV, navOverrides.nav_player), [navOverrides.nav_player])
   const navigate = useNavigate()
   const location = useLocation()
   const title =
@@ -100,7 +109,7 @@ export default function PlayerPortalLayout() {
         </div>
 
         <nav style={{ flex: 1, padding: '14px 12px', display: 'flex', flexDirection: 'column', gap: 4, overflowY: 'auto' }}>
-          {NAV.map((n) => (
+          {nav.map((n) => (
             <NavLink
               key={n.to}
               to={n.to}