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.

frontend/src/lib/xray/inbound-defaults.ts

@@ -263,24 +263,20 @@ export interface WireguardInboundSeed {
   mtu?: number;
   secretKey?: string;
   noKernelTun?: boolean;
-  peerPrivateKey?: string;
 }
 
+// WireGuard is multi-client now: a new inbound holds only the server identity
+// (secretKey/mtu) and starts with no clients. Clients (peers) are added later
+// through the client modal, which generates each one's keypair and a unique
+// tunnel address. peers stays empty for backward-compatible parsing.
 export function createDefaultWireguardInboundSettings(
   seed: WireguardInboundSeed = {},
 ): WireguardInboundSettings {
-  const peerKp = seed.peerPrivateKey
-    ? { privateKey: seed.peerPrivateKey, publicKey: Wireguard.generateKeypair(seed.peerPrivateKey).publicKey }
-    : Wireguard.generateKeypair();
   return {
     mtu: seed.mtu ?? 1420,
     secretKey: seed.secretKey ?? Wireguard.generateKeypair().privateKey,
-    peers: [{
-      privateKey: peerKp.privateKey,
-      publicKey: peerKp.publicKey,
-      allowedIPs: ['10.0.0.2/32'],
-      keepAlive: 0,
-    }],
+    peers: [],
+    clients: [],
     noKernelTun: seed.noKernelTun ?? false,
   };
 }