docs: Task #9 confirmation thresholds + PRD AC updates + API docs

- Update Activity Log with backend@441c8be, frontend@717d5c8
- Update PRD §3 acceptance criteria for Task #9
- Update Payment API.md with confirmation-threshold and awaiting-confirmation endpoints

03 - API Reference/Payment API.md

@@ -464,6 +464,62 @@ Same result shape as above, but for a single destination.
 
 Escrow state (`escrowState`): `unfunded` → `funded` → `released` | `refunded`.
 
+## Confirmation thresholds (admin)
+
+### `GET /api/admin/settings/confirmation-thresholds`
+
+**Auth:** Admin only  
+**Response 200:**
+```json
+{
+  "success": true,
+  "data": [
+    { "chainId": 56, "threshold": 12, "source": "default" },
+    { "chainId": 1, "threshold": 3, "source": "config" }
+  ]
+}
+```
+
+### `PATCH /api/admin/settings/confirmation-thresholds/:chainId`
+
+**Auth:** Admin only  
+**Body:** `{ "threshold": 3 }`  
+**Description:** Updates the runtime confirmation threshold for a chain. The in-memory cache is invalidated immediately so the next `TransactionSafetyProvider` evaluation uses the new value.  
+**Response 200:**
+```json
+{
+  "success": true,
+  "message": "Confirmation threshold for chain 56 updated to 3",
+  "data": { "chainId": 56, "threshold": 3 }
+}
+```
+
+## Payments awaiting confirmation (admin)
+
+### `GET /api/admin/payments/awaiting-confirmation`
+
+**Auth:** Admin only  
+**Query:** `page`, `limit`, `chainId` (optional)  
+**Description:** Lists payments that have an on-chain transaction hash but have not yet reached sufficient confirmations (i.e. `metadata.transactionSafety.status === 'pending'` or `escrowState` is not funded/released/refunded).  
+**Response 200:**
+```json
+{
+  "success": true,
+  "data": [
+    {
+      "_id": "...",
+      "paymentId": "...",
+      "status": "pending",
+      "amount": { "amount": 12.5, "currency": "USDC" },
+      "blockchain": { "network": "bsc", "transactionHash": "0x...", "confirmations": 3 },
+      "metadata": { "transactionSafety": { "status": "pending", "checks": [...] } },
+      "createdAt": "2026-05-28T..."
+    }
+  ],
+  "pagination": { "page": 1, "limit": 25, "total": 4, "totalPages": 1 }
+}
+```
+
 ## Request Network multichain registry (admin)
 
 ### `GET /api/admin/rn/networks`