Issues 19+20: entity-aware schedule import and rollup endpoint

Issue 19:
- entity_id now optional on POST /api/import/schedule
- Resolution: explicit entity_id > name match from row 1 > auto-create
- New params: create_entity_type (default fund), create_vintage_year
- Dry-run reports resolution (will_create/matched/existing)
- Frontend: radio toggle between 'Create from file' and 'Use existing'

Issue 20:
- GET /api/entities/rollup: invested_cents and last_signed_value_cents
  per entity in one pass (SQL aggregates, no waterfall)
- EntitiesList uses rollup instead of N+1 API calls

backend/ten31portal/routers/entity_router.py

@@ -1,17 +1,83 @@
-"""Entity CRUD endpoints."""
+"""Entity CRUD and rollup endpoints."""
 
 from fastapi import APIRouter, Depends, HTTPException
+from pydantic import BaseModel
+from sqlalchemy import func, literal
 from sqlmodel import Session, select
 
 from ten31portal.audit import record_audit
 from ten31portal.auth import get_current_user, require_writer
 from ten31portal.database import get_session
-from ten31portal.models import Entity, EntityStatus, User
+from ten31portal.models import (
+    Entity, EntityStatus, Holding, Position,
+    Valuation, ValuationRound, RoundStatus, User,
+)
 from ten31portal.schemas import EntityCreate, EntityResponse, EntityUpdate
 
 router = APIRouter(prefix="/api/entities", tags=["entities"])
 
 
+class EntityRollupItem(BaseModel):
+    id: int
+    name: str
+    type: str
+    vintage_year: int | None
+    fund_size_cents: int | None
+    status: str
+    invested_cents: int
+    last_signed_value_cents: int
+
+
+@router.get("/rollup")
+def entity_rollup(
+    user: User = Depends(get_current_user),
+    session: Session = Depends(get_session),
+) -> list[EntityRollupItem]:
+    """Per-entity invested and last-signed-value in a single pass."""
+    entities = session.exec(select(Entity)).all()
+    result: list[EntityRollupItem] = []
+
+    for ent in entities:
+        # Sum cost_cents across all positions in this entity's holdings
+        invested_row = session.exec(
+            select(func.coalesce(func.sum(Position.cost_cents), 0))
+            .join(Holding, Position.holding_id == Holding.id)
+            .where(Holding.entity_id == ent.id)
+        ).one()
+        invested_cents = int(invested_row)
+
+        # Find the latest approved round for this entity
+        latest_round = session.exec(
+            select(ValuationRound)
+            .where(
+                ValuationRound.entity_id == ent.id,
+                ValuationRound.status == RoundStatus.approved,
+            )
+            .order_by(ValuationRound.quarter_end.desc())  # type: ignore[union-attr]
+        ).first()
+
+        last_signed_value_cents = 0
+        if latest_round:
+            val_sum = session.exec(
+                select(func.coalesce(func.sum(Valuation.value_cents), 0))
+                .where(Valuation.round_id == latest_round.id)
+            ).one()
+            last_signed_value_cents = int(val_sum)
+
+        result.append(EntityRollupItem(
+            id=ent.id,
+            name=ent.name,
+            type=ent.type.value,
+            vintage_year=ent.vintage_year,
+            fund_size_cents=ent.fund_size_cents,
+            status=ent.status.value,
+            invested_cents=invested_cents,
+            last_signed_value_cents=last_signed_value_cents,
+        ))
+
+    return result
+
+
 @router.get("")
 def list_entities(
     user: User = Depends(get_current_user),