feat: add animated forge/factory hero background with canvas particle system (Closes #850) [fj4WqyCCw3C5ShR1RfB7MoBPTpkRrBFYP1uT35g3MvT]

[waterWang]

Summary

Creates an animated forge/factory-themed hero background for the landing page using Canvas 2D particle system.

Changes

• New: AnimatedHeroBackground.tsx — Canvas-based particle system with:

  • Ember particles (glowing embers floating upward)
  • Spark particles (bright streaks shooting upward)
  • Molten drip particles (slowly falling orange/red droplets)
  • Molten stream effects (vertical dripping streaks)
  • Bottom forge glow (warm orange/purple ambient light from below)
  • Ambient pulsing purple glow
  • Mouse interaction — particles repel from cursor within 120px radius
  • Responsive — recalculates on window resize
  • 60fps — uses requestAnimationFrame with efficient canvas rendering

• Modified: HeroSection.tsx — Replaced simple EmberParticles (5 DOM elements) with full canvas background

• Modified: index.css — Added forge-glow and molten-pulse keyframe animations

• Modified: tailwind.config.js — Added corresponding animation definitions

Performance

• Canvas 2D with max 120 particles, capped spawn rate
• No DOM manipulation per frame (single canvas element)
• Trail effect via semi-transparent fill instead of full clear

Acceptance Criteria

✅ Smooth animations at 60fps on modern browsers
✅ Responsive to different screen sizes
✅ Minimal performance impact

Closes #850

Wallet: fj4WqyCCw3C5ShR1RfB7MoBPTpkRrBFYP1uT35g3MvT