feat(wireguard): multi-client support

WireGuard inbounds now manage per-client peers using xray-core's native WireGuard users (AddUser/RemoveUser). Each client lives in settings.clients (canonical, like every other protocol) and is projected to peers[] only when emitting the xray config, at level 0 so the dispatcher's per-user traffic/online counters work with no extra plumbing.

Backend: internal/util/wireguard gains KeyToHex (base64 to hex for the gRPC path), PublicKeyFromPrivate and GenerateWireguardPSK; xray/api.go builds a wireguard account in AddUser with hex keys (RemoveUser already worked); client CRUD generates a keypair and allocates a unique tunnel address per client and never rotates keys on edit; an idempotent migration converts legacy settings.peers into managed clients; WireGuard is included in the raw subscription.

Frontend: WireGuard in the add-client modal with keys on the credential tab, client schema, per-client QR/link/.conf, inbound form reduced to server settings; i18n added across 13 locales.

Fix: guard the settings[clients] assertion in add/update so a legacy WireGuard inbound stored without a clients key no longer panics.

internal/web/translation/fa-IR.json

@@ -885,6 +885,10 @@
       "uuid": "UUID",
       "flow": "Flow",
       "vmessSecurity": "امنیت VMess",
+      "wireguardPrivateKey": "کلید خصوصی وایرگارد",
+      "wireguardPublicKey": "کلید عمومی وایرگارد",
+      "wireguardPreSharedKey": "کلید پیش‌اشتراکی وایرگارد",
+      "wireguardAllowedIPs": "آی‌پی‌های مجاز وایرگارد",
       "reverseTag": "تگ معکوس",
       "reverseTagPlaceholder": "Reverse tag اختیاری",
       "telegramId": "شناسه کاربر تلگرام",