test(accounts): cover admin add-account endpoint

10 integration tests for POST /api/v1/admin/accounts: unconstrained Open
write + escaped description metadata, explicit-currency path, duplicate->409,
invalid-prefix->400, invalid-characters->400 (parametrized), super-user-only
->403. Adds the add_chart_account helper.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/helpers.py

@@ -13,7 +13,7 @@ separate ISO code field — this matches `models.ExpenseEntry` / `ReceivableEntr
 from decimal import Decimal
 from typing import Any, Optional, Union
 
-from httpx import AsyncClient
+from httpx import AsyncClient, Response
 
 Amount = Union[Decimal, int, float, str]
 
@@ -106,6 +106,26 @@ async def grant_permission(
     return r.json()
 
 
+async def add_chart_account(
+    client: AsyncClient,
+    *,
+    super_user_headers: dict,
+    name: str,
+    description: Optional[str] = None,
+) -> Response:
+    """Super user adds a chart-of-accounts entry via the admin endpoint
+    (POST /api/v1/admin/accounts). Returns the raw Response so callers can
+    assert on status codes (201 / 400 / 409 / 403)."""
+    body: dict[str, Any] = {"name": name}
+    if description is not None:
+        body["description"] = description
+    return await client.post(
+        "/libra/api/v1/admin/accounts",
+        headers=super_user_headers,
+        json=body,
+    )
+
+
 # ---------------------------------------------------------------------------
 # Entries — user side
 # ---------------------------------------------------------------------------