phase-7: code restructure

ui/src/lib/api/index.ts

@@ -0,0 +1,7 @@
+// ── API module barrel ─────────────────────────────────────────────────────
+// Drop-in replacement for the old $lib/api.ts flat file.
+// Existing imports from '$lib/api.js' continue to work via api.ts re-export.
+
+export { screenTickers, fetchCatalysts, analyzeTickers } from './screener.js';
+export { fetchPortfolio, addHolding, removeHolding, fetchMarketContext } from './finance.js';
+export { fetchCalls, fetchCall, createCall, deleteCall, fetchCallsCalendar } from './calls.js';