feat: persist finance daily summaries

backend/app/models/finance_daily_summary.py

@@ -0,0 +1,30 @@
+"""Finance daily summary snapshot model.
+
+Stores pre-computed daily reconciliation results in a single JSON column.
+This keeps the schema stable: adding new summary fields requires no migration.
+"""
+from datetime import date, datetime, timezone
+from typing import Optional
+
+from sqlalchemy import Boolean, Date, DateTime, Integer, Text, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+def _utcnow() -> datetime:
+    return datetime.now(timezone.utc)
+
+
+class FinanceDailySummary(Base):
+    __tablename__ = "finance_daily_summaries"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    stat_date: Mapped[date] = mapped_column(Date, unique=True, nullable=False, index=True)
+    summary_json: Mapped[str] = mapped_column(Text, nullable=False)
+    success: Mapped[bool] = mapped_column(Boolean, default=False, index=True)
+    computed_at: Mapped[datetime] = mapped_column(DateTime, default=_utcnow)
+
+    __table_args__ = (
+        UniqueConstraint("stat_date", name="uq_finance_summary_date"),
+    )