feat(brand): BRAND_* env scheme — instance branding without a rebuild

Replace baked-in UOM/MysticMoon/UOMysticmoon branding with a BRAND_* env
scheme so one prebuilt image runs as any shard; UOMysticmoon becomes the
first tenant that sets these vars rather than a special case in the code.

Architecture (chosen because the app ships as a prebuilt image):
- server/src/config/brand.js + bot/src/brand.js read BRAND_* once at boot,
  with Runic Gateway defaults.
- Text/colors reach the SPA at RUNTIME through the existing public settings
  API (settings.model.getPublic -> SiteContext), so no client rebuild. The
  admin-editable site title + contact email still override BRAND_NAME/email.
- SiteContext applies BRAND_ACCENT_COLOR to the --accent CSS var at runtime.
- Express templates the built index.html <title>/description/OG/favicon at
  serve time from BRAND_* (renderIndexHtml in app.js).
- Server-side consumers read brand directly: emails, TOTP issuer, API docs,
  boot logs, HTML error page. Bot uses it for embed color + logs.

Assets: logo/hero/favicon delivered from a ./brand:/app/brand bind-mount
(BRAND_LOGO/HERO/FAVICON), with neutral defaults baked in; hero falls back
to a built-in image when unset.

Scope: also genericized package.json names (uomysticmoon-* -> runic-gateway-*)
and the DB_NAME/DB_USER/COOKIE_NAME code defaults (runic_gateway/runic/
rg_token). Production keeps its real values by pinning them in .env — see
.env.uomysticmoon.example, which reproduces the exact UOMysticmoon identity
(proof the substitution works). Changing a deployed COOKIE_NAME invalidates
existing sessions, so UOMysticmoon pins uomm_token.

Verified: 193 server tests pass, client builds, app.js loads + templates the
built index.html, brand transform injects title/description/OG/favicon.

server/swagger/swagger.js

@@ -13,6 +13,11 @@
 
 const swaggerAutogen = require('swagger-autogen')({ openapi: '3.0.0' })
 const pkg = require('../package.json')
+const brand = require('../src/config/brand')
+
+// Cookie name is env-configurable (COOKIE_NAME); the spec documents whatever this
+// build targets. This is a build-time artifact — regenerate with `npm run swagger`.
+const COOKIE_NAME = process.env.COOKIE_NAME || 'rg_token'
 
 const outputFile = './swagger/swagger-output.json'
 
@@ -23,13 +28,13 @@ const routes = ['./src/app.js']
 
 const doc = {
   info: {
-    title: 'UOMysticmoon API',
+    title: `${brand.name} API`,
     version: pkg.version,
     description:
-      'REST API for the UOMysticmoon website, wiki and admin panel — a private ' +
+      `REST API for the ${brand.name} website, wiki and admin panel — a private ` +
       'Ultima Online shard.\n\n' +
       '### Authentication\n' +
-      '- **Web / admin panel** uses an httpOnly session cookie (`uomm_token`) issued by ' +
+      `- **Web / admin panel** uses an httpOnly session cookie (\`${COOKIE_NAME}\`) issued by ` +
       '`POST /api/v1/auth/login` (plus `/login/totp` when 2FA is enabled).\n' +
       '- **Native / mobile clients** use bearer access tokens from ' +
       '`POST /api/v1/auth/mobile/login`, refreshed via `/auth/mobile/refresh`.\n\n' +
@@ -67,7 +72,7 @@ const doc = {
       cookieAuth: {
         type: 'apiKey',
         in: 'cookie',
-        name: 'uomm_token',
+        name: COOKIE_NAME,
         description: 'Session JWT set as an httpOnly cookie by POST /api/v1/auth/login.',
       },
       // Native/mobile clients — Authorization: Bearer <accessToken>.
@@ -450,7 +455,7 @@ const doc = {
         type: 'object',
         description: 'Enrollment material returned by POST /account/totp/setup.',
         properties: {
-          otpauthUrl: { type: 'string', example: 'otpauth://totp/UOMysticmoon:admin?secret=...' },
+          otpauthUrl: { type: 'string', example: `otpauth://totp/${brand.name}:admin?secret=...` },
           qr: { type: 'string', description: 'QR code as a data: URL.', example: 'data:image/png;base64,iVBORw0KGgo...' },
         },
       },