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

frontend/src/pages/EntitiesList.tsx

@@ -1,10 +1,16 @@
 import { useEffect, useState } from "react";
 import { Link } from "react-router-dom";
-import { api, type Entity, type EntityType } from "../api";
+import { api, type EntityType } from "../api";
 import { useAuth } from "../context/AuthContext";
 import { formatMoney, formatGainLoss } from "../format";
 
-interface EntityRow extends Entity {
+interface EntityRow {
+  id: number;
+  name: string;
+  type: string;
+  vintage_year: number | null;
+  fund_size_cents: number | null;
+  status: string;
   investedCents: number;
   lastValueCents: number;
 }
@@ -33,32 +39,19 @@ export default function EntitiesList() {
   async function loadData() {
     setLoading(true);
     try {
-      const ents = await api.listEntities();
-      const enriched: EntityRow[] = [];
-
-      for (const ent of ents) {
-        const holdings = await api.listHoldings(ent.id);
-        let investedCents = 0;
-        let lastValueCents = 0;
-
-        for (const h of holdings) {
-          const positions = await api.listPositions(h.id);
-          for (const p of positions) {
-            investedCents += p.cost_cents;
-          }
-        }
-
-        const rounds = await api.listRounds(ent.id);
-        const approved = rounds.filter((r) => r.status === "approved");
-        if (approved.length > 0) {
-          const latest = approved[0];
-          lastValueCents = latest.valuations.reduce((sum, v) => sum + v.value_cents, 0);
-        }
-
-        enriched.push({ ...ent, investedCents, lastValueCents });
-      }
-
-      setEntities(enriched);
+      const rollup = await api.listEntityRollup();
+      setEntities(
+        rollup.map((r) => ({
+          id: r.id,
+          name: r.name,
+          type: r.type,
+          vintage_year: r.vintage_year,
+          fund_size_cents: r.fund_size_cents,
+          status: r.status,
+          investedCents: r.invested_cents,
+          lastValueCents: r.last_signed_value_cents,
+        })),
+      );
     } finally {
       setLoading(false);
     }