fix: address account valuation review findings

dashboard/page_views/accounts.py

@@ -30,6 +30,12 @@ ACCOUNT_TYPE_STYLES = {
     "other": "#57606a",
 }
 
+
+def _account_balance_basis_date(account: dict[str, Any]) -> str:
+    """Return only an explicit evidence date, never a sync timestamp."""
+    return str(account.get("last_balance_basis_date") or "")[:10]
+
+
 def render_accounts_list_header(items: list[dict[str, Any]]) -> None:
     st.markdown(
         f'{len(items)}개 계좌',
@@ -113,14 +119,19 @@ def account_edit_dialog(account: dict[str, Any], db_path: str) -> None:
             format_func=lambda value: ACCOUNT_TYPE_LABELS[value],
         )
 
-        balance_columns = st.columns(2)
+        balance_columns = st.columns(3)
         last_balance_raw = balance_columns[0].text_input(
             "기준 잔액",
             value="" if account.get("last_balance") is None else str(account.get("last_balance")),
             help="원 단위 정수",
         )
-        last_synced_at = balance_columns[1].text_input(
-            "기준 시각",
+        last_balance_basis_date = balance_columns[1].text_input(
+            "잔액 기준일",
+            value=account.get("last_balance_basis_date") or "",
+            help="실제 증빙 기준일(YYYY-MM-DD). 미상인 경우 비워 둡니다.",
+        )
+        last_synced_at = balance_columns[2].text_input(
+            "동기화 시각",
             value=account.get("last_synced_at") or "",
             help="예: 2026-08-20 또는 2026-08-20T23:59:00+09:00",
         )
@@ -156,6 +167,7 @@ def account_edit_dialog(account: dict[str, Any], db_path: str) -> None:
             institution=institution,
             type=account_type,
             last_balance=last_balance,
+            last_balance_basis_date=last_balance_basis_date,
             last_synced_at=last_synced_at,
             statement_status=statement_status,
             liquidity_bucket=liquidity_bucket,
@@ -184,7 +196,7 @@ def page_accounts(db_path: str) -> None:
             st.dataframe(valuations, width="stretch", hide_index=True)
             # The list is historical insertion order; a rejected/corrected
             # tail is not necessarily the effective current valuation.
-            basis = (selected_account.get("last_synced_at") or "")[:10]
+            basis = _account_balance_basis_date(selected_account)
             selected = accounts_gateway.select_account_valuation(selected_id, basis, as_of=True, db_path=db_path) if basis else {}
             selected_valuation = selected.get("valuation") if selected.get("success") else None
             latest = selected_valuation or next(
@@ -195,7 +207,7 @@ def page_accounts(db_path: str) -> None:
             st.warning("평가 이력이 없습니다.")
         with st.expander("계좌 평가 등록"):
             with st.form(f"account_valuation_register_{selected_id}"):
-                v_date = st.text_input("평가 기준일", value=selected_account.get("last_synced_at", "")[:10])
+                v_date = st.text_input("평가 기준일", value=_account_balance_basis_date(selected_account))
                 v_amount = st.number_input("평가 금액", value=int(selected_account.get("last_balance") or 0), step=1)
                 default_kind = "loan_balance" if selected_account.get("type") == "loan" else ("total_value" if selected_account.get("type") == "investment" else "cash_balance")
                 v_kind = st.selectbox("평가 종류", ["cash_balance", "balance", "total_value", "loan_balance", "loan"], index=["cash_balance", "balance", "total_value", "loan_balance", "loan"].index(default_kind))