chore: update Dockerfile for pnpm, modify package.json dependencies, and implement rate limiting

- Switched from npm to pnpm for dependency management in Dockerfile, improving build efficiency.
- Updated Vue and Vue Router versions in package.json for better compatibility.
- Changed placeholder URLs in site.ts to actual Fiverr links and adjusted review count.
- Removed obsolete sitemap.xml file to streamline the project.
- Added a new rate limiting plugin to manage API request limits for the contact endpoint.

server/plugins/rate-limit.ts

@@ -0,0 +1,32 @@
+const ipMap = new Map<string, { count: number; reset: number }>()
+
+// Clean stale entries every 5 minutes to prevent memory leak
+setInterval(() => {
+  const now = Date.now()
+  for (const [ip, entry] of ipMap) {
+    if (entry.reset < now) ipMap.delete(ip)
+  }
+}, 5 * 60 * 1000)
+
+export default defineNitroPlugin((nitro) => {
+  nitro.hooks.hook('request', (event) => {
+    // Only rate-limit the contact POST endpoint
+    if (event.method !== 'POST' || !event.path.startsWith('/api/contact')) return
+
+    const ip = getRequestIP(event, { xForwardedFor: true }) ?? 'unknown'
+    const now = Date.now()
+    const window = 60_000 // 1 minute window
+    const limit = 3 // max 3 requests per minute per IP
+
+    const entry = ipMap.get(ip)
+    if (!entry || entry.reset < now) {
+      ipMap.set(ip, { count: 1, reset: now + window })
+      return
+    }
+
+    entry.count++
+    if (entry.count > limit) {
+      throw createError({ statusCode: 429, message: 'Too many requests. Please try again later.' })
+    }
+  })
+})