feat: initialize Next.js project with database schema

- Set up Next.js with App Router, TypeScript, Tailwind CSS
- Configure shadcn/ui with dark theme
- Install dependencies: lightweight-charts, papaparse, lucide-react
- Set up Drizzle ORM with better-sqlite3
- Create database schema for candles and annotations tables
- Generate migration SQL

src/lib/db/index.ts

@@ -0,0 +1,15 @@
+import Database from 'better-sqlite3';
+import { drizzle } from 'drizzle-orm/better-sqlite3';
+import * as schema from './schema';
+import path from 'path';
+import fs from 'fs';
+
+// Ensure data directory exists
+const dataDir = path.join(process.cwd(), 'data');
+if (!fs.existsSync(dataDir)) {
+  fs.mkdirSync(dataDir, { recursive: true });
+}
+
+const dbPath = path.join(dataDir, 'candles.db');
+const sqlite = new Database(dbPath);
+export const db = drizzle(sqlite, { schema });