GST Billing Website & App

I’m building a complete GST-compliant billing solution that works both as a responsive website and an Android APK. The platform must be multi-tenant because several independent businesses will run their own accounts under one roof, each with isolated data and branding.

Core workflow
• Create professional GST invoices that can be viewed, downloaded as PDF, or sent to a printer in a single click.
• Track sales, purchase expenses, and automatically generate real-time GST reports (GSTR-1, GSTR-3B, etc.).
• Maintain catalogs of products, customers, suppliers, and payment records with simple CRUD screens.

Technical expectations
• Modern tech stack you’re comfortable with (Laravel / Node / Django, React / Vue, or similar) paired with a robust relational database.
• Secure multi-tenant architecture, role-based access, and GST fields hard-coded to Indian tax rules.
• Clean, responsive UI and a lightweight Android APK (targeting Android 8+) built from the same codebase or a dedicated mobile framework such as Flutter / React Native.
• Output invoices in standard A4 and thermal printer sizes; fonts and GST breakup must match govt guidelines.

Deliverables
1. Fully deployed web app (domain + SSL) and published APK.
2. Super-admin panel to onboard new businesses, manage plans, and view system metrics.
3. Tenant admin panel for each business with dashboards, search, filters, and CSV/PDF exports.
4. Complete source code, build scripts, and a concise setup/readme.
5. Demo data and a short walkthrough video.

Acceptance criteria
• I can spin up a new business tenant in under 2 minutes without touching code.
• Invoice download/print works flawlessly on Chrome, Firefox, Edge, and common Android devices.
• All GST totals match manual calculations within one paise.
• No critical bugs during a 48-hour live test with sample traffic.

Timeline: I need the first deployable version ASAP, so please outline an aggressive but realistic schedule with interim milestones for my approval.