fix(accounts): recover ledger-only account instead of blanket 409 (libra-#50)

When add_account reported the Open already existed, the endpoint raised
409 before the DB-mirror step — so an account present in the ledger but
missing from libra's DB (a prior sync failure with no cross-DB atomicity,
or an out-of-band open) was stranded: invisible to permissions with no
recovery path. Now 409 only when the account is already in the DB too;
otherwise sync it and return success. Adds a recovery test.

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

tests/test_admin_chart_accounts_api.py

@@ -93,6 +93,32 @@ async def test_add_chart_account_duplicate_returns_409(
     assert "already exists" in second.json().get("detail", "").lower()
 
 
+@pytest.mark.anyio
+async def test_add_chart_account_recovers_ledger_only_account(
+    client, super_user_headers,
+):
+    """An account present in the ledger but absent from libra's DB (prior sync
+    failure / out-of-band edit) is recovered (synced), not 409'd — otherwise it
+    would be permanently un-grantable with no path back.
+
+    Reproduce the ledger-only state by creating normally (so Fava parses the
+    Open) then deleting only the libra-DB row — appending to the ledger file
+    directly would race Fava's parse cache."""
+    from ..crud import db  # the same singleton the app uses
+
+    name = _unique("Expenses:Recover")
+    first = await add_chart_account(client, super_user_headers=super_user_headers, name=name)
+    assert first.status_code == 201, f"setup create failed: {first.status_code} {first.text}"
+
+    await db.execute("DELETE FROM accounts WHERE name = :name", {"name": name})
+
+    r = await add_chart_account(client, super_user_headers=super_user_headers, name=name)
+    assert r.status_code == 201, f"expected 201 recovery, got {r.status_code}: {r.text}"
+    body = r.json()
+    assert body.get("already_existed") is True, body
+    assert body["synced_to_libra_db"] is True, body
+
+
 @pytest.mark.anyio
 async def test_add_chart_account_invalid_prefix_returns_400(
     client, super_user_headers, fava_ledger_path,