chore: extract arcade into standalone repo

Arcade lives as its own pnpm workspace at ~/Documents/Code/arcade
now, with no @mana/* coupling. This drops every reference and the
games/ directory from the monorepo.

Removes:
- games/ directory (89 files: web + server + 22 HTML games + screenshots)
- @arcade/web, @arcade/server pnpm workspace entries (games/* globs)
- arcade scripts in root package.json (4 scripts)
- arcade.mana.how from mana-auth trusted origins + CORS_ORIGINS
- arcade entries in mana-apps registry, app-icons, URL overrides
- arcade.mana.how from cloudflared tunnel + prometheus blackbox probes
- arcade-web service block in docker-compose.macmini.yml
- generate-env.mjs entries for arcade server + web
- BRANDING_ONLY 'arcade' entry in registry consistency spec
- dead arcade translation keys in GuestWelcomeModal (DE+EN)
- arcade mention in CLAUDE.md, authentication guideline, MODULE_REGISTRY

Verified:
- services/mana-auth/src/auth/sso-config.spec.ts: 8/8 pass
- pnpm install regenerates lockfile cleanly (-536 lines)
- no remaining 'arcade' refs outside historical snapshot docs

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docker-compose.macmini.yml

@@ -296,7 +296,7 @@ services:
       # Enforced by services/mana-auth/src/auth/sso-config.spec.ts.
       # All productivity modules now live under mana.how (path-based) —
       # no per-module subdomain entries required here.
-      CORS_ORIGINS: https://mana.how,https://auth.mana.how,https://arcade.mana.how,https://whopxl.mana.how
+      CORS_ORIGINS: https://mana.how,https://auth.mana.how,https://whopxl.mana.how
     ports:
       - "3001:3001"
     healthcheck:
@@ -1028,33 +1028,7 @@ services:
   # uload-web, memoro-web
 
   # picture-backend: REMOVED — replaced by Hono server (apps/picture/apps/server)
-
-  arcade-web:
-    build:
-      context: .
-      dockerfile: games/arcade/apps/web/Dockerfile
-    image: arcade-web:local
-    container_name: mana-app-arcade-web
-    restart: always
-    mem_limit: 128m
-    depends_on:
-      mana-auth:
-        condition: service_healthy
-    environment:
-      NODE_ENV: production
-      PORT: 5210
-      PUBLIC_MANA_AUTH_URL: http://mana-auth:3001
-      PUBLIC_MANA_AUTH_URL_CLIENT: https://auth.mana.how
-      PUBLIC_SYNC_SERVER_URL: http://mana-sync:3010
-      PUBLIC_SYNC_SERVER_URL_CLIENT: https://sync.mana.how
-    ports:
-      - "5210:5210"
-    healthcheck:
-      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://127.0.0.1:5210/health"]
-      interval: 180s
-      timeout: 10s
-      retries: 3
-      start_period: 20s
+  # arcade-web: REMOVED — extracted to standalone repo at ~/Documents/Code/arcade
 
   manavoxel-web:
     build:
@@ -1756,7 +1730,7 @@ services:
       # as the rest of the platform.
       DATABASE_URL: postgresql://postgres:${POSTGRES_PASSWORD:-mana123}@postgres:5432/mana_platform
       # CORS — only the unified mana.how origin needs access today.
-      # The arcade + manavoxel game frontends don't call apps/api.
+      # The manavoxel game frontend doesn't call apps/api.
       CORS_ORIGINS: https://mana.how
       # Structured-logger format
       LOGGER_FORMAT: json