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>

views_api.py

@@ -3055,3 +3055,83 @@ async def api_get_account_hierarchy(
     accounts_with_hierarchy.sort(key=lambda a: a.name)
 
     return accounts_with_hierarchy
+
+
+# ===== ACCOUNT SYNC ENDPOINTS =====
+
+
+@castle_api_router.post("/api/v1/admin/accounts/sync")
+async def api_sync_all_accounts(
+    force_full_sync: bool = False,
+    wallet: WalletTypeInfo = Depends(require_admin_key),
+) -> dict:
+    """
+    Sync all accounts from Beancount to Castle DB (admin only).
+
+    This ensures Castle DB has metadata entries for all accounts that exist
+    in Beancount, enabling permissions and user associations to work properly.
+
+    Args:
+        force_full_sync: If True, re-check all accounts. If False, only add new ones.
+
+    Returns:
+        Sync statistics: {total_beancount_accounts, accounts_added, accounts_skipped, errors}
+    """
+    from .account_sync import sync_accounts_from_beancount
+
+    logger.info(f"Admin {wallet.wallet.user[:8]} triggered account sync (force={force_full_sync})")
+
+    try:
+        stats = await sync_accounts_from_beancount(force_full_sync=force_full_sync)
+        logger.info(f"Account sync complete: {stats['accounts_added']} added, {stats['accounts_skipped']} skipped")
+        return stats
+    except Exception as e:
+        logger.error(f"Account sync failed: {e}")
+        raise HTTPException(
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+            detail=f"Account sync failed: {str(e)}"
+        )
+
+
+@castle_api_router.post("/api/v1/admin/accounts/sync/{account_name:path}")
+async def api_sync_single_account(
+    account_name: str,
+    wallet: WalletTypeInfo = Depends(require_admin_key),
+) -> dict:
+    """
+    Sync a single account from Beancount to Castle DB (admin only).
+
+    Useful for ensuring a specific account exists in Castle DB before
+    granting permissions on it.
+
+    Args:
+        account_name: Hierarchical account name (e.g., "Expenses:Food:Groceries")
+
+    Returns:
+        {success: bool, account_name: str, message: str}
+    """
+    from .account_sync import sync_single_account_from_beancount
+
+    logger.info(f"Admin {wallet.wallet.user[:8]} triggered sync for account: {account_name}")
+
+    try:
+        created = await sync_single_account_from_beancount(account_name)
+
+        if created:
+            return {
+                "success": True,
+                "account_name": account_name,
+                "message": f"Account '{account_name}' synced successfully"
+            }
+        else:
+            return {
+                "success": False,
+                "account_name": account_name,
+                "message": f"Account '{account_name}' already exists or not found in Beancount"
+            }
+    except Exception as e:
+        logger.error(f"Single account sync failed for {account_name}: {e}")
+        raise HTTPException(
+            status_code=HTTPStatus.INTERNAL_SERVER_ERROR,
+            detail=f"Account sync failed: {str(e)}"
+        )