s-ui-x-extended v1.0.0-beta5

Pre-release. Unifies the navigation menu across the two UI environments. The
Classic and Nexus shells previously kept independent, hand-maintained
menu lists that had drifted apart — Providers showed only in Classic, Paid
Subscriptions only in Nexus. Both shells now read a single shared source, so the
tabs stay in sync and neither environment can silently lose one again.

Highlights

• One menu, both environments. New frontend/src/layouts/menu.ts is the
  single source of truth; the Classic drawer and the Nexus sidebar both import it.
  nexusMenu.ts becomes a thin backward-compatible re-export, and the nexus-only
  singBoxSettings metadata now lives in the shared list.
• Tabs reconciled. Classic and Nexus now expose the same 16 tabs in the same
  order — Classic gains Paid Subscriptions, Nexus gains Providers.
  /migrate-xui stays a contextual page reached from the Backup dialog, not a
  top-level tab.
• Localization parity. Providers / Paid Subscriptions are now translated
  in zh-Hans, zh-Hant, Persian and Vietnamese instead of falling back to English.
• Drift-guard test pins the menu's paths, order, uniqueness and the nexus
  sing-box surfaces so the two environments can't diverge again unnoticed.

See CHANGELOG.md for the full bilingual list and
SECURITY.md for supply-chain and hardening notes. This is a
pre-release — review SECURITY.md before exposing the panel.