feat: add top monthly sold by category analysis pipeline

- Introduces a new script to discover categories and identify products with high monthly sales volume.
- Filters candidates based on sellability status and a configurable monthly sold threshold.
- Enriches product data with Keepa and SP-API metrics before performing LLM-based analysis.
- Persists results to SQLite and includes unit tests for the core processing logic.

package.json

@@ -5,6 +5,7 @@
   "private": true,
   "scripts": {
     "bestsellers": "bun run src/bestsellers-by-category.ts",
+    "monthly-sold": "bun run src/top-monthly-sold-by-category.ts",
     "start": "bun run src/index.ts",
     "start:web": "bun --hot src/server.ts",
     "build:web": "bun build src/web/index.html --outdir dist",