feat(extensions): add NIP-15 marketplace extension

Implements a Nostr-native marketplace extension for Lightning.Pub
that is compatible with NIP-15 (Nostr Marketplace).

Features:
- Stall management (kind 30017 events)
- Product listings (kind 30018 events)
- Order processing via encrypted Nostr DMs or RPC
- Multi-currency support with exchange rate caching
- Inventory management with stock tracking
- Customer relationship management
- Lightning payment integration

The extension leverages Lightning.Pub's existing Nostr infrastructure
for a more elegant implementation than traditional HTTP-based approaches.

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

src/extensions/context.ts

@@ -8,7 +8,8 @@ import {
   PaymentReceivedData,
   NostrEvent,
   UnsignedNostrEvent,
-  RpcMethodHandler
+  RpcMethodHandler,
+  LnurlPayInfo
 } from './types.js'
 
 /**
@@ -44,6 +45,15 @@ export interface MainHandlerInterface {
       paymentHash: string
       feeSats: number
     }>
+
+    /**
+     * Get LNURL-pay info for a user by their Nostr pubkey
+     * This enables Lightning Address (LUD-16) and zap (NIP-57) support
+     */
+    getLnurlPayInfoByPubkey(pubkeyHex: string, options?: {
+      metadata?: string
+      description?: string
+    }): Promise<LnurlPayInfo>
   }
 
   // Nostr operations
@@ -177,6 +187,17 @@ export class ExtensionContextImpl implements ExtensionContext {
     return this.mainHandler.sendNostrEvent(event)
   }
 
+  /**
+   * Get LNURL-pay info for a user by pubkey
+   * Enables Lightning Address and zap support
+   */
+  async getLnurlPayInfo(pubkeyHex: string, options?: {
+    metadata?: string
+    description?: string
+  }): Promise<LnurlPayInfo> {
+    return this.mainHandler.paymentManager.getLnurlPayInfoByPubkey(pubkeyHex, options)
+  }
+
   /**
    * Subscribe to payment received callbacks
    */

src/extensions/types.ts

@@ -77,6 +77,20 @@ export interface PaymentReceivedData {
   metadata?: Record<string, any>
 }
 
+/**
+ * LNURL-pay info response (LUD-06/LUD-16)
+ * Used for Lightning Address and zap support
+ */
+export interface LnurlPayInfo {
+  tag: 'payRequest'
+  callback: string                // URL to call with amount
+  minSendable: number             // Minimum msats
+  maxSendable: number             // Maximum msats
+  metadata: string                // JSON-encoded metadata array
+  allowsNostr?: boolean           // Whether zaps are supported
+  nostrPubkey?: string            // Pubkey for zap receipts (hex)
+}
+
 /**
  * Nostr event structure (minimal)
  */
@@ -142,6 +156,15 @@ export interface ExtensionContext {
    */
   publishNostrEvent(event: UnsignedNostrEvent): Promise<string | null>
 
+  /**
+   * Get LNURL-pay info for a user (by pubkey)
+   * Used to enable Lightning Address support (LUD-16) and zaps (NIP-57)
+   */
+  getLnurlPayInfo(pubkeyHex: string, options?: {
+    metadata?: string              // Custom metadata JSON
+    description?: string           // Human-readable description
+  }): Promise<LnurlPayInfo>
+
   /**
    * Subscribe to payment received callbacks
    */