feat: add software_hashes table schema and reimport pipeline

- Add softwareHashes Drizzle model (download_id PK, md5, crc32,
  size_bytes, inner_path, updated_at)
- Update import_mysql.sh to reimport from JSON snapshot after DB wipe
- Add pnpm scripts: update:hashes, export:hashes
- Create data/zxdb/ directory for JSON snapshot storage

claude-opus-4-6@MacFiver

package.json

@@ -10,6 +10,8 @@
     "deploy": "bin/deploy.sh",
     "deploy:branch": "bin/deploy.sh",
     "setup:zxdb-local": "bin/setup-zxdb-local.sh",
+    "update:hashes": "node bin/update-software-hashes.mjs",
+    "export:hashes": "node bin/update-software-hashes.mjs --export-only",
     "deploy-prod": "git push --set-upstream explorer.specnext.dev deploy",
     "deploy-test": "git push --set-upstream test.explorer.specnext.dev test"
   },