feat(proxy): add proxy pool and per-connection binding + strictProxy support

- Centralize proxy management with reusable proxy pools
- Per-connection proxy binding with legacy fallback
- Add strictProxy option: fail hard instead of silently falling back to direct
- Resolve alicode-intl conflict: keep alicode-intl support + proxy support

Made-with: Cursor

src/shared/components/Sidebar.js

@@ -12,6 +12,7 @@ import { ConfirmModal } from "./Modal";
 const navItems = [
   { href: "/dashboard/endpoint", label: "Endpoint", icon: "api" },
   { href: "/dashboard/providers", label: "Providers", icon: "dns" },
+  { href: "/dashboard/proxy-pools", label: "Proxy Pools", icon: "lan" },
   { href: "/dashboard/combos", label: "Combos", icon: "layers" },
   { href: "/dashboard/usage", label: "Usage", icon: "bar_chart" },
   { href: "/dashboard/quota", label: "Quota Tracker", icon: "data_usage" },