feat(theming): settings-store, nav merge util and radius tokens

Phases 0-2 of docs/website/THEMING_AND_NAV.md. Groundwork only: no admin UI,
no consumer wiring, and an instance that never touches the new settings keys
renders exactly as it does today.

Phase 0 - settings store:
- settingsDb.remove() and DELETE /api/v1/admin/settings/:key, the "reset to
  default" primitive. Defaults for these keys live in BRAND_* env, theme.css
  and the hardcoded NAV arrays, so reset has to delete the row rather than
  store a copy of the default. Allowlisted to the five theming/nav keys plus
  hero_layout_draft, admin-only, idempotent.
- GET /api/v1/settings/nav behind requireAuth with no role gate. AdminLayout
  renders for editors and moderators and PlayerPortalLayout for players, and
  none of them can read GET /admin/settings, so without this their nav
  override would silently never apply.
- A fifth router group for it: /public is anonymous, /admin/settings is
  adminOnly, /player is self-scoped data. This is configuration that needs a
  login.
- parseJsonSetting() in utils/settingsJson.js. settings.value is TEXT, so
  every JSON key arrives as a string; malformed or wrong-shaped reads as
  absent, never as an error and never half-applied.
- theme_visual / brand_assets / nav_public join PUBLIC_KEYS; nav_admin and
  nav_player deliberately do not.

Phase 1 - client/src/lib/navOverrides.js, the pure merge util. Presentation
only: it can set label/order/hidden and (grouped navs) group, and nothing
else. It cannot introduce a `to`, cannot touch roles/feature, and hidden:false
cannot un-hide anything - the existing filters run afterward, unchanged, and
remain the boundary.

Phase 2 - promoted 23 border-radius literals in theme.css to four tokens at
today's values (14x8px, 4x999px, 4x10px, 1x12px). The 7px/6px editor chrome
and the two 50% circles stay literal. --shadow-card and --panel-grad were
already tokens.

Tests: 16 new server tests, 20 new client tests. The route-manifest guard now
also asserts /settings/** sits behind requireAuth. Swagger and both route
artifacts regenerated.

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

server/swagger/swagger.js

@@ -59,6 +59,7 @@ const doc = {
     { name: 'Player', description: 'Self-service player accounts (register, credentials, 2FA, linked identities)' },
     { name: 'Player · Shard', description: 'Link an in-game account and read its roster / vendors (uo-link)' },
     { name: 'Player · Appeals', description: 'Player-submitted moderation appeals' },
+    { name: 'Settings', description: 'Site-wide settings any authenticated account may read (nav overrides)' },
     { name: 'Admin · Dashboard', description: 'Dashboard summary and site mode' },
     { name: 'Admin · Posts', description: 'News / five-on-friday / newsletter / screenshots + uploads' },
     { name: 'Admin · Wiki', description: 'Wiki pages, categories, tags and revisions' },
@@ -778,6 +779,19 @@ const doc = {
         },
         additionalProperties: true,
       },
+      NavSettings: {
+        type: 'object',
+        description:
+          'Nav overrides for the two authenticated layouts (GET /settings/nav). Each value is the stored JSON **string** — settings.value is TEXT — or null when that nav was never overridden. Parse fail-safe: treat malformed as absent and fall back to the hardcoded nav.',
+        properties: {
+          nav_admin: {
+            type: 'string',
+            nullable: true,
+            example: '{"/admin/posts":{"label":"Blog Posts","order":10}}',
+          },
+          nav_player: { type: 'string', nullable: true, example: null },
+        },
+      },
       // Delete/mutation acknowledgements — each echoes the affected resource key
       // or a boolean flag rather than a { message } string.
       DeletedId: {