Reapply "Redesign finance dashboard with period summaries"

This reverts commit da14ec5740.

backend/app/routers/finance.py

@@ -11,6 +11,7 @@ from sqlalchemy.orm import Session
 from app.database import get_db
 from app.services.finance_service import (
     compute_daily_summary,
+    get_finance_summary,
     get_or_create_daily_summary,
     overwrite_daily_summary,
     today_shanghai,
@@ -53,6 +54,26 @@ def daily_summary(
     return get_or_create_daily_summary(db, target)
 
 
+@router.get("/summary")
+def finance_summary(
+    period: str = Query("day", description="day | week | month"),
+    date: str | None = Query(None, description="YYYY-MM-DD, defaults to yesterday Asia/Shanghai"),
+    db: Session = Depends(get_db),
+    _: Any = Depends(get_current_user),
+) -> dict:
+    """Return finance summary for day/week/month.
+
+    day reuses the existing daily snapshot behavior. week/month aggregate only
+    stored finance_daily_summaries rows and never call upstream services.
+    """
+    period = period.lower()
+    if period not in {"day", "week", "month"}:
+        raise HTTPException(400, f"Invalid period: {period!r}. Expected day, week, or month.")
+    target = _resolve_date(date)
+    _validate_not_future(target)
+    return get_finance_summary(db, period, target)
+
+
 @router.post("/daily-summary/compare")
 def compare_daily_summary(
     date: str | None = Query(None, description="YYYY-MM-DD, defaults to yesterday Asia/Shanghai"),