secure-frontend.md


This is a very large multi-part question. Let me build a comprehensive interactive guide for you as a visual reference.Here's a summary of everything covered across the 6 tabs:

**Tier mechanisms tab** — each tier's exact mechanism is explained step by step, with why each layer works and what its specific weakness is. Click any tier card to expand it.

**Beginner steps tab** — walks you from "open VS Code" through every file you need to create, what to type in the terminal, and why each step exists. No assumed knowledge.

**Tier 2 + Firebase tab** — the most detailed section. Goes from creating a Google account → Firebase project → Firestore database → security rules → connecting your HTML app → local fingerprint combo → deploying. Copy-paste ready code at every step.

**HTML app security tab** — covers your meals/weight tracker specifically. Ranks attack vectors by real-world risk (XSS is your biggest threat, not hackers breaking encryption), gives exact code fixes for each, and compares every free hosting option.

**VPS protection tab** — ordered checklist for your 2GB/8CPU server. SSH hardening, firewall, Fail2ban, Nginx rate limiting, Certbot SSL, and Cloudflare free proxy. Do them in order shown — top items are most urgent.

**Data collection tab** — compares Telegram Bot, Firebase, Google Sheets, Supabase, and REDCap for academic research. Includes the consent UI code (legally required for health data) and the anonymisation pattern that makes collected data ethically usable.

The most important single piece of advice: for your HTML health app, **add Cloudflare as a proxy in front of your VPS** — it's free and immediately gives you DDoS protection, bot filtering, and hides your server's real IP address, which covers the majority of "expert attacker" scenarios you mentioned.