Integrate account sync with API, background tasks, and user creation

Integration Components:
1. Manual API Endpoints (admin-only):
   - POST /api/v1/admin/accounts/sync (full sync)
   - POST /api/v1/admin/accounts/sync/{account_name} (single account)

2. Scheduled Background Sync:
   - Hourly background task (wait_for_account_sync)
   - Registered in castle_start() lifecycle
   - Automatically syncs new accounts from Beancount to Castle DB

3. Auto-sync on User Account Creation:
   - Updated get_or_create_user_account() in crud.py
   - Uses sync_single_account_from_beancount() for consistency
   - Ensures receivable/payable accounts are synced when users register

Flow:
- User associates wallet → creates receivable/payable in Beancount
  → syncs to Castle DB → permissions can be granted
- Admin manually syncs → all Beancount accounts added to Castle DB
- Hourly task → catches any accounts created directly in Beancount

This ensures Beancount remains the source of truth while Castle DB
maintains metadata for permissions and user associations.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

__init__.py

@@ -36,6 +36,7 @@ def castle_start():
     from lnbits.tasks import create_permanent_unique_task
     from .fava_client import init_fava_client
     from .models import CastleSettings
+    from .tasks import wait_for_account_sync
 
     # Initialize Fava client with default settings
     # (Will be re-initialized if admin updates settings)
@@ -55,5 +56,10 @@ def castle_start():
     task = create_permanent_unique_task("ext_castle", wait_for_paid_invoices)
     scheduled_tasks.append(task)
 
+    # Start account sync task (runs hourly)
+    sync_task = create_permanent_unique_task("ext_castle_account_sync", wait_for_account_sync)
+    scheduled_tasks.append(sync_task)
+    logger.info("Castle account sync task started (runs hourly)")
+
 
 __all__ = ["castle_ext", "castle_static_files", "db", "castle_start", "castle_stop"]