Add intent ID generation for purchase requests

FEATURE: Unique Order/Intent ID
- Generate intent ID format: pi_<buyerPubkey8>_<timestamp>
- Example: pi_8f7a9b2c_1761034427234
- Ties order to buyer (first 8 chars of pubkey)
- Sortable by timestamp
- Included in encrypted purchase intent message

Technical Changes:
- Add intentId field to PurchaseIntent interface
- Update preparePurchaseIntent() to accept buyerPubkey parameter
- Get buyer pubkey from signer.getPublicKey() before preparing messages
- Intent ID logged for tracking in service logs

Benefits:
- Both buyer and seller can reference same order ID
- Traceable in logs and conversation history
- Unique identifier before Nostr event ID exists
- Helps with order management and support

Author: psam21

src/services/business/PurchaseBusinessService.ts

@@ -159,14 +159,19 @@ export class PurchaseBusinessService {
    * Prepare purchase intent message content
    * 
    * @param sellerIntent - Purchase intent for a specific seller
+   * @param buyerPubkey - Buyer's public key for generating intent ID
    * @returns JSON string for NIP-17 message content
    */
-  public preparePurchaseIntent(sellerIntent: PurchaseIntentBySeller): string {
+  public preparePurchaseIntent(sellerIntent: PurchaseIntentBySeller, buyerPubkey: string): string {
+    const timestamp = Date.now();
+    const intentId = `pi_${buyerPubkey.slice(0, 8)}_${timestamp}`;
+    
     const intent: PurchaseIntent = {
       type: 'purchase-intent',
+      intentId,
       products: sellerIntent.products,
       totalSats: sellerIntent.totalSats,
-      timestamp: Date.now(),
+      timestamp,
     };
 
     const messageContent = JSON.stringify(intent, null, 2);
@@ -177,6 +182,7 @@ export class PurchaseBusinessService {
       sellerPubkey: sellerIntent.sellerPubkey,
       productCount: sellerIntent.products.length,
       totalSats: sellerIntent.totalSats,
+      intentId,
     });
 
     return messageContent;
@@ -220,6 +226,9 @@ export class PurchaseBusinessService {
     // Group by seller
     const sellerGroups = this.groupBySeller(items);
 
+    // Get buyer pubkey for intent ID generation
+    const buyerPubkey = await signer.getPublicKey();
+
     // Send to each seller
     const results: PurchaseIntentResult['details'] = [];
     let successCount = 0;
@@ -229,8 +238,8 @@ export class PurchaseBusinessService {
       const sellerGroup = sellerGroups[i];
 
       try {
-        // Prepare message content
-        const messageContent = this.preparePurchaseIntent(sellerGroup);
+        // Prepare message content with intent ID
+        const messageContent = this.preparePurchaseIntent(sellerGroup, buyerPubkey);
 
         // Send encrypted message via NIP-17
         const sendResult = await this.messagingService.sendMessage(

src/types/purchase.ts

@@ -38,6 +38,9 @@ export interface PurchaseIntent {
   /** Message type identifier */
   type: 'purchase-intent';
 
+  /** Unique intent ID for tracking (format: pi_<pubkey8>_<timestamp>) */
+  intentId: string;
+  
   /** Array of products being purchased from this seller */
   products: PurchaseIntentItem[];