Creates accounts in Fava if they don't exist

This change ensures that user-specific accounts are automatically created
in the Fava/Beancount ledger when they are first requested. It checks for
the existence of the account via a Fava query and creates it via an Open
directive if it's missing.  This simplifies account management and
ensures that all necessary accounts are available for transactions.

This implementation adds a new `add_account` method to the `FavaClient`
class which makes use of the /add_entries endpoint to create an account
using an Open Directive.

crud.py

@@ -2,6 +2,7 @@ import json
 from datetime import datetime
 from typing import Optional
 
+import httpx
 from lnbits.db import Database
 from lnbits.helpers import urlsafe_short_hash
 
@@ -96,6 +97,10 @@ async def get_or_create_user_account(
     """
     Get or create a user-specific account with hierarchical naming.
 
+    This function checks if the account exists in Fava/Beancount and creates it
+    if it doesn't exist. The account is also registered in Castle's database for
+    metadata tracking (permissions, descriptions, etc.).
+
     Examples:
         get_or_create_user_account("af983632", AccountType.ASSET, "Accounts Receivable")
         → "Assets:Receivable:User-af983632"
@@ -104,11 +109,13 @@ async def get_or_create_user_account(
         → "Liabilities:Payable:User-af983632"
     """
     from .account_utils import format_hierarchical_account_name
+    from .fava_client import get_fava_client
+    from loguru import logger
 
     # Generate hierarchical account name
     account_name = format_hierarchical_account_name(account_type, base_name, user_id)
 
-    # Try to find existing account with this hierarchical name
+    # Try to find existing account with this hierarchical name in Castle DB
     account = await db.fetchone(
         """
         SELECT * FROM accounts
@@ -119,7 +126,42 @@ async def get_or_create_user_account(
     )
 
     if not account:
-        # Create new account with hierarchical name
+        # Check if account exists in Fava/Beancount
+        fava = get_fava_client()
+        try:
+            # Query Fava for this account
+            query = f"SELECT account WHERE account = '{account_name}'"
+            async with httpx.AsyncClient(timeout=5.0) as client:
+                response = await client.get(
+                    f"{fava.base_url}/query",
+                    params={"query_string": query}
+                )
+                response.raise_for_status()
+                result = response.json()
+
+                # Check if account exists in Fava
+                fava_has_account = len(result.get("data", {}).get("rows", [])) > 0
+
+                if not fava_has_account:
+                    # Create account in Fava/Beancount via Open directive
+                    logger.info(f"Creating account in Fava: {account_name}")
+                    await fava.add_account(
+                        account_name=account_name,
+                        currencies=["EUR", "SATS", "USD"],  # Support common currencies
+                        metadata={
+                            "user_id": user_id,
+                            "description": f"User-specific {account_type.value} account"
+                        }
+                    )
+                    logger.info(f"Created account in Fava: {account_name}")
+                else:
+                    logger.info(f"Account already exists in Fava: {account_name}")
+
+        except Exception as e:
+            logger.warning(f"Could not check/create account in Fava: {e}")
+            # Continue anyway - account creation in Castle DB is still useful for metadata
+
+        # Create account in Castle DB for metadata tracking
         account = await create_account(
             CreateAccount(
                 name=account_name,