feat: implement SQLite persistent storage for analysis results

- Implemented database initialization and connection management in `database.ts` using Bun's SQLite.
- Created `runs` and `results` tables to track historical analysis metadata and detailed product performance.
- Updated `writer.ts` to persist analysis results to the database within a transaction, replacing the previous CSV output logic.
- Updated README and `.gitignore` to reflect the new persistent storage capability.

.gitignore

@@ -35,3 +35,9 @@ report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
 *.xlsx
 *.csv
 
+
+results.db
+
+results.db-shm
+
+results.db-wal