Adds on-chain Bitcoin payment support

Adds support for on-chain Bitcoin payments by:
- Introducing a new `Assets:Bitcoin:OnChain` account.
- Updating the `SettleReceivable` and `PayUser` models to include `txid` for storing transaction IDs.
- Modifying the API endpoints to handle `btc_onchain` as a valid payment method and associate it with the new account.

This allows tracking on-chain Bitcoin transactions separately from Lightning Network payments.

views_api.py

@@ -786,7 +786,7 @@ async def api_settle_receivable(
         )
 
     # Validate payment method
-    valid_methods = ["cash", "bank_transfer", "check", "other"]
+    valid_methods = ["cash", "bank_transfer", "check", "lightning", "btc_onchain", "other"]
     if data.payment_method.lower() not in valid_methods:
         raise HTTPException(
             status_code=HTTPStatus.BAD_REQUEST,
@@ -803,6 +803,8 @@ async def api_settle_receivable(
         "cash": "Cash",
         "bank_transfer": "Bank Account",
         "check": "Bank Account",
+        "lightning": "Assets:Bitcoin:Lightning",
+        "btc_onchain": "Assets:Bitcoin:OnChain",
         "other": "Cash"
     }
 
@@ -852,6 +854,14 @@ async def api_settle_receivable(
         amount_in_sats = int(data.amount)
         line_metadata = {}
 
+    # Add payment hash for lightning payments
+    if data.payment_hash:
+        line_metadata["payment_hash"] = data.payment_hash
+
+    # Add transaction ID for on-chain Bitcoin payments
+    if data.txid:
+        line_metadata["txid"] = data.txid
+
     # Add meta information for audit trail
     entry_meta = {
         "source": "manual_settlement",
@@ -924,7 +934,7 @@ async def api_pay_user(
         )
 
     # Validate payment method
-    valid_methods = ["cash", "bank_transfer", "check", "lightning", "other"]
+    valid_methods = ["cash", "bank_transfer", "check", "lightning", "btc_onchain", "other"]
     if data.payment_method.lower() not in valid_methods:
         raise HTTPException(
             status_code=HTTPStatus.BAD_REQUEST,
@@ -937,43 +947,31 @@ async def api_pay_user(
     )
 
     # Get the appropriate asset account based on payment method
-    if data.payment_method.lower() == "lightning":
-        # For lightning, use the Lightning Wallet account
-        payment_account = await get_account_by_name("Lightning Wallet")
-        if not payment_account:
-            # Create it if it doesn't exist
-            payment_account = await create_account(
-                CreateAccount(
-                    name="Lightning Wallet",
-                    account_type=AccountType.ASSET,
-                    description="Lightning Network wallet for Castle",
-                ),
-                wallet.wallet.id,
-            )
-    else:
-        # For cash/bank/check
-        payment_account_map = {
-            "cash": "Cash",
-            "bank_transfer": "Bank Account",
-            "check": "Bank Account",
-            "other": "Cash"
-        }
-        account_name = payment_account_map.get(data.payment_method.lower(), "Cash")
-        payment_account = await get_account_by_name(account_name)
+    payment_account_map = {
+        "cash": "Cash",
+        "bank_transfer": "Bank Account",
+        "check": "Bank Account",
+        "lightning": "Assets:Bitcoin:Lightning",
+        "btc_onchain": "Assets:Bitcoin:OnChain",
+        "other": "Cash"
+    }
 
-        if not payment_account:
-            # Try to find any asset account
-            all_accounts = await get_all_accounts()
-            for acc in all_accounts:
-                if acc.account_type == AccountType.ASSET and "receivable" not in acc.name.lower():
-                    payment_account = acc
-                    break
+    account_name = payment_account_map.get(data.payment_method.lower(), "Cash")
+    payment_account = await get_account_by_name(account_name)
 
-        if not payment_account:
-            raise HTTPException(
-                status_code=HTTPStatus.NOT_FOUND,
-                detail=f"Payment account '{account_name}' not found. Please create it first.",
-            )
+    if not payment_account:
+        # Try to find any asset account that's not receivable
+        all_accounts = await get_all_accounts()
+        for acc in all_accounts:
+            if acc.account_type == AccountType.ASSET and "receivable" not in acc.name.lower():
+                payment_account = acc
+                break
+
+    if not payment_account:
+        raise HTTPException(
+            status_code=HTTPStatus.NOT_FOUND,
+            detail=f"Payment account '{account_name}' not found. Please create it first.",
+        )
 
     # Determine the amount to record in the journal
     # IMPORTANT: Always record in satoshis to match the payable account balance
@@ -1003,6 +1001,10 @@ async def api_pay_user(
     if data.payment_hash:
         line_metadata["payment_hash"] = data.payment_hash
 
+    # Add transaction ID for on-chain Bitcoin payments
+    if data.txid:
+        line_metadata["txid"] = data.txid
+
     # Create journal entry
     # DR Accounts Payable (liability decreased), CR Cash/Lightning/Bank (asset decreased)
     # This records that castle paid its debt