Add WireGuard VPN with random /31 subnet isolation (v0.40.0)

- Add embedded WireGuard VPN server using wireguard-go + netstack
- Implement deterministic /31 subnet allocation from seed + sequence
- Use Badger's built-in Sequence for atomic counter allocation
- Add NIP-46 bunker server for remote signing over VPN
- Add revoked key tracking and access audit logging for users
- Add Bunker tab to web UI with WireGuard/bunker QR codes
- Support key regeneration with old keypair archiving

New environment variables:
- ORLY_WG_ENABLED: Enable WireGuard VPN server
- ORLY_WG_PORT: UDP port for WireGuard (default 51820)
- ORLY_WG_ENDPOINT: Public endpoint for WireGuard
- ORLY_WG_NETWORK: Base network for subnet pool (default 10.0.0.0/8)
- ORLY_BUNKER_ENABLED: Enable NIP-46 bunker
- ORLY_BUNKER_PORT: WebSocket port for bunker (default 3335)

Files added:
- pkg/wireguard/: WireGuard server, keygen, subnet pool, errors
- pkg/bunker/: NIP-46 bunker server and session handling
- pkg/database/wireguard.go: Peer storage with audit logging
- app/handle-wireguard.go: API endpoints for config/regenerate/audit
- app/wireguard-helpers.go: Key derivation helpers
- app/web/src/BunkerView.svelte: Bunker UI with QR codes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/wireguard-helpers.go

@@ -0,0 +1,19 @@
+package app
+
+import (
+	"golang.org/x/crypto/curve25519"
+
+	"git.mleku.dev/mleku/nostr/crypto/keys"
+)
+
+// derivePublicKey derives a Curve25519 public key from a private key.
+func derivePublicKey(privateKey []byte) ([]byte, error) {
+	publicKey := make([]byte, 32)
+	curve25519.ScalarBaseMult((*[32]byte)(publicKey), (*[32]byte)(privateKey))
+	return publicKey, nil
+}
+
+// deriveSecp256k1PublicKey derives a secp256k1 public key from a secret key.
+func deriveSecp256k1PublicKey(secretKey []byte) ([]byte, error) {
+	return keys.SecretBytesToPubKeyBytes(secretKey)
+}