chore: remove obsolete Android app configuration files

- Deleted build.gradle.kts, gradle.properties, and gradlew files as part of the cleanup process.
- Removed local.properties and various generated files from the .gradle directory to streamline the project structure.
- Cleared out unnecessary build artifacts and intermediate files to improve project maintainability.

backend/package.json

@@ -29,6 +29,7 @@
     "node-cron": "^4.2.1",
     "node-fetch": "^3.3.2",
     "nodemailer": "^8.0.4",
+    "pdf-lib": "^1.17.1",
     "pdf-parse": "^1.1.1",
     "pdfjs-dist": "^5.4.394",
     "playwright": "^1.58.2",