Add Cashu blind signature access tokens (NIP-XX draft)

Implements privacy-preserving bearer tokens for relay access control using
Cashu-style blind signatures. Tokens prove whitelist membership without
linking issuance to usage.

Features:
- BDHKE crypto primitives (HashToCurve, Blind, Sign, Unblind, Verify)
- Keyset management with weekly rotation
- Token format with kind permissions and scope isolation
- Generic issuer/verifier with pluggable authorization
- HTTP endpoints: POST /cashu/mint, GET /cashu/keysets, GET /cashu/info
- ACL adapter bridging ORLY's access control to Cashu AuthzChecker
- Stateless revocation via ACL re-check on each token use
- Two-token rotation for seamless renewal (max 2 weeks after blacklist)

Configuration:
- ORLY_CASHU_ENABLED: Enable Cashu tokens
- ORLY_CASHU_TOKEN_TTL: Token validity (default: 1 week)
- ORLY_CASHU_SCOPES: Allowed scopes (relay, nip46, blossom, api)
- ORLY_CASHU_REAUTHORIZE: Re-check ACL on each verification

Files:
- pkg/cashu/bdhke/: Core blind signature cryptography
- pkg/cashu/keyset/: Keyset management and rotation
- pkg/cashu/token/: Token format with kind permissions
- pkg/cashu/issuer/: Token issuance with authorization
- pkg/cashu/verifier/: Token verification with middleware
- pkg/interfaces/cashu/: AuthzChecker, KeysetStore interfaces
- pkg/bunker/acl_adapter.go: ORLY ACL integration
- app/handle-cashu.go: HTTP endpoints
- docs/NIP-XX-CASHU-ACCESS-TOKENS.md: Full specification

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

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

app/server.go

@@ -34,6 +34,8 @@ import (
 	"next.orly.dev/pkg/protocol/nip43"
 	"next.orly.dev/pkg/protocol/publish"
 	"next.orly.dev/pkg/bunker"
+	"next.orly.dev/pkg/cashu/issuer"
+	"next.orly.dev/pkg/cashu/verifier"
 	"next.orly.dev/pkg/ratelimit"
 	"next.orly.dev/pkg/spider"
 	dsync "next.orly.dev/pkg/sync"
@@ -85,6 +87,10 @@ type Server struct {
 	wireguardServer *wireguard.Server
 	bunkerServer    *bunker.Server
 	subnetPool      *wireguard.SubnetPool
+
+	// Cashu access token system (NIP-XX)
+	CashuIssuer   *issuer.Issuer
+	CashuVerifier *verifier.Verifier
 }
 
 // isIPBlacklisted checks if an IP address is blacklisted using the managed ACL system
@@ -350,6 +356,14 @@ func (s *Server) UserInterface() {
 	s.mux.HandleFunc("/api/wireguard/status", s.handleWireGuardStatus)
 	s.mux.HandleFunc("/api/wireguard/audit", s.handleWireGuardAudit)
 	s.mux.HandleFunc("/api/bunker/url", s.handleBunkerURL)
+
+	// Cashu access token endpoints (NIP-XX)
+	s.mux.HandleFunc("/cashu/mint", s.handleCashuMint)
+	s.mux.HandleFunc("/cashu/keysets", s.handleCashuKeysets)
+	s.mux.HandleFunc("/cashu/info", s.handleCashuInfo)
+	if s.CashuIssuer != nil {
+		log.Printf("Cashu access token API enabled at /cashu")
+	}
 }
 
 // handleFavicon serves orly-favicon.png as favicon.ico