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/lib/db.server.ts

@@ -0,0 +1,15 @@
+import { PrismaClient } from "@prisma/client";
+
+declare global {
+  var prisma: PrismaClient | undefined;
+}
+
+const prismaClientSingleton = () => {
+  return new PrismaClient();
+};
+
+export const db = global.prisma || prismaClientSingleton();
+
+if (process.env.NODE_ENV !== "production") {
+  global.prisma = db;
+}