Add test data generation script for Umami analytics

- Create generate-test-data.js script for generating realistic demo data
- Support for small (3 days), medium (14 days), and full (30 days) scales
- Generates realistic user sessions, pageviews, custom events, and revenue
- Includes geographic diversity, device variety, and traffic source distributions
- Implements proper UTM campaign tracking and conversion funnels
- Uses direct Prisma writes for performance (~10k sessions in 5 minutes)
- Add npm script: 'generate-test-data' for easy execution

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

package.json

@@ -33,6 +33,7 @@
     "check-db": "node scripts/check-db.js",
     "check-env": "node scripts/check-env.js",
     "copy-db-files": "node scripts/copy-db-files.js",
+    "generate-test-data": "node scripts/generate-test-data.js",
     "extract-messages": "formatjs extract \"src/components/messages.ts\" --out-file build/extracted-messages.json",
     "merge-messages": "node scripts/merge-messages.js",
     "generate-lang": "npm-run-all extract-messages merge-messages",