feat: add stock database with prisma for portfolio persistence

- Initialize Prisma with SQLite and Stock model
- Create database service layer with singleton client
- Add API routes for stock CRUD operations
- Integrate database with analyze page to persist ticker entries
- Add Playwright tests for stock database functionality

app/routes/api/stocks/index.ts

@@ -0,0 +1,22 @@
+import { db } from "../../../lib/db.server";
+
+export async function loader() {
+  const stocks = await db.stock.findMany({
+    orderBy: { ticker: "asc" },
+  });
+  return Response.json(stocks);
+}
+
+export async function action({ request }: { request: Request }) {
+  const formData = await request.formData();
+  const ticker = formData.get("ticker")?.toString().toUpperCase();
+
+  if (!ticker) {
+    return Response.json({ error: "Ticker is required" }, { status: 400 });
+  }
+
+  const stock = await db.stock.create({
+    data: { ticker },
+  });
+  return Response.json(stock);
+}