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

prisma/schema.prisma

@@ -5,6 +5,7 @@ generator client {
 
 datasource db {
   provider = "sqlite"
+  url      = "file:./dev.db"
 }
 
 model Stock {