fix: resolve Web UI display issues (#365)

## Fixes

### 1. Typewriter Component - Missing First Character
- Fix character loss issue where first character of each line was missing
- Add proper state reset logic before starting typing animation
- Extract character before setState to avoid closure issues
- Add setTimeout(0) to ensure state is updated before typing starts
- Change dependency from `lines` to `sanitizedLines` for correct updates
- Use `??` instead of `||` for safer null handling

### 2. Chinese Translation - Leading Spaces
- Remove leading spaces from startupMessages1/2/3 in Chinese translations
- Ensures proper display of startup messages in terminal simulation

### 3. Dynamic GitHub Stats with Animation
- Add useGitHubStats hook to fetch real-time GitHub repository data
- Add useCounterAnimation hook with easeOutExpo easing for smooth number animation
- Display dynamic star count with smooth counter animation (2s duration)
- Display dynamic days count (static, no animation)
- Support bilingual display (EN/ZH) with proper formatting

## Changes
- web/src/components/Typewriter.tsx: Fix first character loss bug
- web/src/i18n/translations.ts: Remove leading spaces in Chinese messages
- web/src/components/landing/HeroSection.tsx: Add dynamic GitHub stats
- web/src/hooks/useGitHubStats.ts: New hook for GitHub API integration
- web/src/hooks/useCounterAnimation.ts: New hook for number animations

Fixes #365

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

web/src/hooks/useCounterAnimation.ts

@@ -0,0 +1,51 @@
+import { useEffect, useState } from 'react'
+
+interface UseCounterAnimationOptions {
+  start?: number
+  end: number
+  duration?: number
+  decimals?: number
+}
+
+export function useCounterAnimation({
+  start = 0,
+  end,
+  duration = 2000,
+  decimals = 0,
+}: UseCounterAnimationOptions): number {
+  const [count, setCount] = useState(start)
+
+  useEffect(() => {
+    if (end === 0) return
+
+    let startTime: number | null = null
+    let animationFrame: number
+
+    const animate = (currentTime: number) => {
+      if (startTime === null) startTime = currentTime
+      const progress = Math.min((currentTime - startTime) / duration, 1)
+
+      // 使用 easeOutExpo 缓动函数，让数字快速启动后缓慢停止
+      const easeOutExpo = progress === 1 ? 1 : 1 - Math.pow(2, -10 * progress)
+
+      const currentCount = start + (end - start) * easeOutExpo
+      setCount(currentCount)
+
+      if (progress < 1) {
+        animationFrame = requestAnimationFrame(animate)
+      } else {
+        setCount(end)
+      }
+    }
+
+    animationFrame = requestAnimationFrame(animate)
+
+    return () => {
+      if (animationFrame) {
+        cancelAnimationFrame(animationFrame)
+      }
+    }
+  }, [start, end, duration])
+
+  return decimals > 0 ? parseFloat(count.toFixed(decimals)) : Math.floor(count)
+}

web/src/hooks/useGitHubStats.ts

@@ -0,0 +1,61 @@
+import { useState, useEffect } from 'react'
+
+interface GitHubStats {
+  stars: number
+  forks: number
+  createdAt: string
+  daysOld: number
+  isLoading: boolean
+  error: string | null
+}
+
+export function useGitHubStats(owner: string, repo: string): GitHubStats {
+  const [stats, setStats] = useState<GitHubStats>({
+    stars: 0,
+    forks: 0,
+    createdAt: '',
+    daysOld: 0,
+    isLoading: true,
+    error: null,
+  })
+
+  useEffect(() => {
+    const fetchGitHubStats = async () => {
+      try {
+        const response = await fetch(`https://api.github.com/repos/${owner}/${repo}`)
+
+        if (!response.ok) {
+          throw new Error('Failed to fetch GitHub stats')
+        }
+
+        const data = await response.json()
+
+        // Calculate days since creation
+        const createdDate = new Date(data.created_at)
+        const now = new Date()
+        const diffTime = Math.abs(now.getTime() - createdDate.getTime())
+        const diffDays = Math.ceil(diffTime / (1000 * 60 * 60 * 24))
+
+        setStats({
+          stars: data.stargazers_count,
+          forks: data.forks_count,
+          createdAt: data.created_at,
+          daysOld: diffDays,
+          isLoading: false,
+          error: null,
+        })
+      } catch (error) {
+        console.error('Error fetching GitHub stats:', error)
+        setStats(prev => ({
+          ...prev,
+          isLoading: false,
+          error: error instanceof Error ? error.message : 'Unknown error',
+        }))
+      }
+    }
+
+    fetchGitHubStats()
+  }, [owner, repo])
+
+  return stats
+}