feat(nip05): add Lightning Address support for zaps

Adds /.well-known/lnurlp/:username endpoint that:
1. Looks up username in NIP-05 database
2. Gets LNURL-pay info from Lightning.Pub for that user
3. Returns standard LUD-16 response for wallet compatibility

This makes NIP-05 addresses (alice@domain) work seamlessly as
Lightning Addresses for receiving payments and NIP-57 zaps.

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

src/extensions/nip05/index.ts

@@ -94,6 +94,13 @@ export default class Nip05Extension implements Extension {
         method: 'GET',
         path: '/api/v1/nip05/nostr.json',
         handler: this.handleNostrJson.bind(this)
+      },
+      // Lightning Address endpoint (LUD-16)
+      // Makes NIP-05 usernames work as Lightning Addresses for zaps
+      {
+        method: 'GET',
+        path: '/.well-known/lnurlp/:username',
+        handler: this.handleLnurlPay.bind(this)
       }
     ]
   }
@@ -220,6 +227,72 @@ export default class Nip05Extension implements Extension {
       }
     }
   }
+
+  /**
+   * Handle /.well-known/lnurlp/:username request (Lightning Address / LUD-16)
+   *
+   * This enables NIP-05 usernames to work as Lightning Addresses for receiving
+   * payments and zaps. When someone sends to alice@domain.com:
+   * 1. Wallet resolves /.well-known/lnurlp/alice
+   * 2. We look up alice -> pubkey in our NIP-05 database
+   * 3. We return LNURL-pay info from Lightning.Pub for that user
+   */
+  private async handleLnurlPay(req: HttpRequest): Promise<HttpResponse> {
+    try {
+      const { username } = req.params
+      const appId = req.headers['x-application-id'] || 'default'
+
+      if (!username) {
+        return {
+          status: 400,
+          body: { status: 'ERROR', reason: 'Username required' },
+          headers: {
+            'Content-Type': 'application/json',
+            'Access-Control-Allow-Origin': '*'
+          }
+        }
+      }
+
+      // Look up the username in our NIP-05 database
+      const lookup = await this.manager.lookupUsername(appId, username)
+
+      if (!lookup.found || !lookup.identity) {
+        return {
+          status: 404,
+          body: { status: 'ERROR', reason: 'User not found' },
+          headers: {
+            'Content-Type': 'application/json',
+            'Access-Control-Allow-Origin': '*'
+          }
+        }
+      }
+
+      // Get LNURL-pay info from Lightning.Pub for this user's pubkey
+      const lnurlPayInfo = await this.ctx.getLnurlPayInfo(lookup.identity.pubkey_hex, {
+        description: `Pay to ${username}`
+      })
+
+      return {
+        status: 200,
+        body: lnurlPayInfo,
+        headers: {
+          'Content-Type': 'application/json',
+          'Access-Control-Allow-Origin': '*',
+          'Cache-Control': 'max-age=60' // Cache for 1 minute
+        }
+      }
+    } catch (error) {
+      this.ctx.log('error', `Error handling lnurlp: ${error}`)
+      return {
+        status: 500,
+        body: { status: 'ERROR', reason: 'Internal server error' },
+        headers: {
+          'Content-Type': 'application/json',
+          'Access-Control-Allow-Origin': '*'
+        }
+      }
+    }
+  }
 }
 
 // Export types for external use