Refactor database interactions to use Drizzle ORM

- Replaced direct SQLite database calls with Drizzle ORM methods in `top-monthly-sold-by-category.ts`, `writer.ts`, and `upc-file-analysis.ts`.
- Updated test cases in `top-monthly-sold-by-category.test.ts` to mock the new database interactions.
- Removed unnecessary database initialization and cleanup code.
- Improved code readability and maintainability by using ORM features for inserting and updating records.

drizzle.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from "drizzle-kit";
+
+export default defineConfig({
+  schema: "./src/db/schema.ts",
+  out: "./drizzle",
+  dialect: "postgresql",
+  dbCredentials: {
+    url: process.env.DB_CONNECTION_STRING!,
+  },
+});