chore: rewrite hero/about copy, add favicon and polish portfolio

[anhvuFE]

Summary

• Replace generic "passionate about clean code / Agile environments" hero and About copy with concrete one-liners
• Generate a favicon set (32/64/180/192/512 PNG + apple-touch-icon) from the avatar; drop unused boxicons + unicons CDN links
• Move EmailJS keys to REACT_APP_* env vars; commit .env.example, gitignore .env
• Fix small audit findings (year hardcoding, missing aria-labels, missing subject field, stale browserslist)
• Rewrite README and remove the deploy.txt scratchpad

Copy changes

Where	Before	After
Home description	"Full Stack Developer with 3+ years of experience... Passionate about clean code, intuitive design, and delivering high-quality products in Agile environments."	"I build fast, accessible web apps with React, TypeScript and Node. Currently shipping at neliSoftwares — open to freelance and full-time roles."
Typewriter roles	..."React & TypeScript Expert"	..."Frontend-leaning Engineer", "React & TypeScript"
About paragraph 1	"I am a Developer with over two years of experience..."	"Three years in, four companies, mostly shipping React and TypeScript..."
About paragraph 2	"I am comfortable working with RESTful APIs, state management, and building clean, scalable interfaces..."	"I care about the boring details that make products feel good — small bundles, fast loads, accessible interactions..."
Contact subtitle	"Have a project in mind or just want to say hello?"	"Hiring, freelance, or just curious about something I built — drop a message."
Years experience	3+	4+ (Home stats, About achievement, Info card, bento About preview)

Head and PWA

• public/index.html: set title (Vũ Xuân Anh — Full Stack Developer), theme-color, meta description, favicon links and apple-touch-icon
• public/manifest.json (new): name, icons, standalone display, theme/background colors
• public/robots.txt, public/sitemap.xml (new)
• Removed unused boxicons and unicons CDN <link>s (render-blocking, no usage)

Environment / config

• Contact form now reads REACT_APP_EMAILJS_SERVICE_ID, REACT_APP_EMAILJS_TEMPLATE_ID, REACT_APP_EMAILJS_PUBLIC_KEY from env, with a friendly error if missing
• .env.example checked in; .env added to .gitignore
• Subject field is now passed to EmailJS template params (was being collected but dropped)
• caniuse-lite updated via update-browserslist-db

Other

• Footer.tsx: currentYear now uses new Date().getFullYear()
• Certificate.tsx and Services.tsx: aria-label added to modal close IconButtons
• README.md rewritten: stack, layout, local dev, env vars, build/deploy, image pipeline, structure
• deploy.txt removed
• scripts/generate-favicon.js (new): regenerates the favicon set from src/assets/avatar.jpg

Test plan

• npm run dev — favicon shows the avatar in the browser tab
• Hero shows the new copy; typewriter cycles through the new roles
• About 'My Journey' shows the rewritten paragraphs
• All counters show "4+ Years"
• Open contact form, submit empty -> per-field errors; submit a valid form -> success snackbar; subject field arrives in the EmailJS test
• Mobile install prompt picks up manifest.json (DevTools > Application > Manifest)
• npm run build succeeds