Secure Invoice Web + Android

I need a full-fledged invoicing solution that works in the browser and is paired with a dedicated Android app. Think of the overall polish and flow found in SleekBill or myBillBook, then add stronger data security and cloud-based sync so my team can work from anywhere without fear of losing records.

Core modules
• Invoice generation with GST discounts, and branded PDF export
• Expense tracking that ties directly into profit & loss views
• Client management with searchable contacts, notes, and activity timelines
• Cloud storage so every invoice, receipt, and client detail is backed up automatically and stays in sync between web and Android

Key requirements
• Single sign-on between web portal and Android app
• Role-based access and encryption at rest & in transit
• Responsive web UI (desktop + tablet)
• Clean, intuitive Android experience that mirrors the web features offline and syncs once online
• Downloadable reports (CSV, PDF) and a simple dashboard for quick stats

Acceptance criteria
1. I can log in on the web, create an invoice, then see the same record in the Android app within seconds.
2. No unauthenticated request should expose data during a basic penetration test.
3. First paid invoice can be generated, saved to cloud, and emailed to a test customer within three clicks.

Source code, build scripts, and a short deployment guide should be delivered at hand-off so I can host the web app on my own server and publish the Android build to the Play Store.