feat: migrate from SQLite to PostgreSQL - complete schema and API updates

- Remove better-sqlite3, add pg driver
- Convert schema to PostgreSQL types (serial, timestamp, boolean, jsonb)
- Generate fresh PostgreSQL migrations
- Update database connection layer with pg.Pool
- Fix all API routes: remove JSON.parse/stringify, use native timestamps and booleans
- Update drizzle.config.ts and .env.example for PostgreSQL

src/lib/db/index.ts

@@ -1,28 +1,30 @@
-import Database from 'better-sqlite3';
-import { drizzle } from 'drizzle-orm/better-sqlite3';
-import { migrate } from 'drizzle-orm/better-sqlite3/migrator';
+import { Pool } from 'pg';
+import { drizzle } from 'drizzle-orm/node-postgres';
+import { migrate } from 'drizzle-orm/node-postgres/migrator';
 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 });
+// Read DATABASE_URL from environment
+const DATABASE_URL = process.env.DATABASE_URL;
+
+if (!DATABASE_URL) {
+  throw new Error('DATABASE_URL environment variable is not set');
 }
 
-const dbPath = path.join(dataDir, 'candles.db');
-const sqlite = new Database(dbPath);
-export const db = drizzle(sqlite, { schema });
+// Create PostgreSQL connection pool
+const pool = new Pool({
+  connectionString: DATABASE_URL,
+  max: 10,
+});
 
-// Run migrations at startup (for local dev).
-// In Docker, migrations are run by scripts/run-migrations.js before the app starts,
-// so this will be a no-op (all migrations already applied).
+export const db = drizzle(pool, { schema });
+
+// Run migrations at startup (skip during build phase)
 const isBuildTime = process.env.NEXT_PHASE === 'phase-production-build' || process.env.NEXT_PHASE === 'phase-development-build';
 
 if (!isBuildTime) {
   try {
-    migrate(db, { migrationsFolder: path.join(process.cwd(), 'drizzle') });
+    await migrate(db, { migrationsFolder: path.join(process.cwd(), 'drizzle') });
     console.log('✅ Database migrations completed');
   } catch (error) {
     console.error('❌ Migration failed:', error);