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/agents/sentiment.ts

@@ -16,7 +16,7 @@ export class SentimentAnalyst {
 
   constructor(client: OpenRouterClient, config?: SentimentConfig) {
     this.client = client;
-    this.model = config?.model ?? "google/gemini-2.0-flash-exp:free";
+    this.model = config?.model ?? "openai/gpt-oss-120b:free";
   }
 
   getModel(): string {