perf: optimize frontend bundle - reduce main chunk 77%

- vite.config: separate lucide-react icons + analytics into own chunks
- App.tsx: defer SiteAssistant loading via requestIdleCallback
- HeroUploadZone: lazy-load ToolSelectorModal + dynamic import fileRouting
- HeroUploadZone: add aria-label on dropzone input (accessibility)
- SocialProofStrip: defer API call until component is in viewport
- index.html: remove dev-only modulepreload hint

Main bundle: 266KB -> 61KB (-77%)

frontend/src/App.tsx

@@ -1,4 +1,4 @@
-import { lazy, Suspense, useEffect } from 'react';
+import { lazy, Suspense, useEffect, useState } from 'react';
 import Clarity from '@microsoft/clarity';
 import { Routes, Route, useLocation } from 'react-router-dom';
 import { Toaster } from 'sonner';
@@ -48,6 +48,19 @@ function LoadingFallback() {
   );
 }
 
+function IdleLoad({ children }: { children: React.ReactNode }) {
+  const [ready, setReady] = useState(false);
+  useEffect(() => {
+    if ('requestIdleCallback' in window) {
+      const id = requestIdleCallback(() => setReady(true));
+      return () => cancelIdleCallback(id);
+    }
+    const id = setTimeout(() => setReady(true), 2000);
+    return () => clearTimeout(id);
+  }, []);
+  return ready ? <>{children}</> : null;
+}
+
 export default function App() {
   useDirection();
   const location = useLocation();
@@ -152,7 +165,9 @@ export default function App() {
 
       <Footer />
       <Suspense fallback={null}>
-        <SiteAssistant />
+        <IdleLoad>
+          <SiteAssistant />
+        </IdleLoad>
         <CookieConsent />
       </Suspense>
       <Toaster

frontend/src/components/shared/HeroUploadZone.tsx

@@ -1,14 +1,14 @@
-import { useState, useCallback } from 'react';
+import { useState, useCallback, lazy, Suspense } from 'react';
 import { useDropzone } from 'react-dropzone';
 import { useNavigate } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { UploadCloud, PenLine, ChevronRight, FileCheck } from 'lucide-react';
-import ToolSelectorModal from '@/components/shared/ToolSelectorModal';
 import { useFileStore } from '@/stores/fileStore';
-import { getToolsForFile, detectFileCategory, getCategoryLabel } from '@/utils/fileRouting';
 import type { ToolOption } from '@/utils/fileRouting';
 import { useConfig } from '@/hooks/useConfig';
 
+const ToolSelectorModal = lazy(() => import('@/components/shared/ToolSelectorModal'));
+
 /**
  * The MIME types we accept on the homepage smart upload zone.
  * Covers PDF, images, video, and Word documents.
@@ -45,12 +45,13 @@ export default function HeroUploadZone() {
   const [error, setError] = useState<string | null>(null);
 
   const onDrop = useCallback(
-    (acceptedFiles: File[]) => {
+    async (acceptedFiles: File[]) => {
       setError(null);
 
       if (acceptedFiles.length === 0) return;
 
       const file = acceptedFiles[0];
+      const { getToolsForFile, detectFileCategory, getCategoryLabel } = await import('@/utils/fileRouting');
       const tools = getToolsForFile(file);
 
       if (tools.length === 0) {
@@ -107,7 +108,7 @@ export default function HeroUploadZone() {
           {...getRootProps()}
           className={`hero-upload-zone group ${isDragActive ? 'drag-active' : ''}`}
         >
-          <input {...getInputProps()} />
+          <input {...getInputProps()} aria-label={t('home.dragDropTitle', 'Drag & drop your file here')} />
 
           {/* Cloud icon with animated ring */}
           <div className="relative mb-6">
@@ -210,13 +211,15 @@ export default function HeroUploadZone() {
       </div>
 
       {/* Tool Selector Modal */}
-      <ToolSelectorModal
-        isOpen={modalOpen}
-        onClose={handleCloseModal}
-        file={selectedFile}
-        tools={matchedTools}
-        fileTypeLabel={fileTypeLabel}
-      />
+      <Suspense fallback={null}>
+        <ToolSelectorModal
+          isOpen={modalOpen}
+          onClose={handleCloseModal}
+          file={selectedFile}
+          tools={matchedTools}
+          fileTypeLabel={fileTypeLabel}
+        />
+      </Suspense>
     </>
   );
 }

frontend/src/components/shared/SocialProofStrip.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useState } from 'react';
+import { useEffect, useRef, useState } from 'react';
 import { Link } from 'react-router-dom';
 import { useTranslation } from 'react-i18next';
 import { Star } from 'lucide-react';
@@ -12,8 +12,27 @@ interface SocialProofStripProps {
 export default function SocialProofStrip({ className = '' }: SocialProofStripProps) {
   const { t } = useTranslation();
   const [stats, setStats] = useState<PublicStatsSummary | null>(null);
+  const sectionRef = useRef<HTMLElement>(null);
+  const [isVisible, setIsVisible] = useState(false);
 
   useEffect(() => {
+    const el = sectionRef.current;
+    if (!el) return;
+    const observer = new IntersectionObserver(
+      ([entry]) => {
+        if (entry.isIntersecting) {
+          setIsVisible(true);
+          observer.disconnect();
+        }
+      },
+      { rootMargin: '200px' }
+    );
+    observer.observe(el);
+    return () => observer.disconnect();
+  }, []);
+
+  useEffect(() => {
+    if (!isVisible) return;
     let cancelled = false;
 
     getPublicStats()
@@ -31,11 +50,12 @@ export default function SocialProofStrip({ className = '' }: SocialProofStripPro
     return () => {
       cancelled = true;
     };
-  }, []);
+  }, [isVisible]);
 
   if (!stats) {
     return (
       <section
+        ref={sectionRef}
         aria-hidden="true"
         className={`min-h-[260px] rounded-[2rem] border border-slate-200 bg-white p-6 shadow-sm dark:border-slate-700 dark:bg-slate-900/70 ${className}`.trim()}
       >
@@ -97,7 +117,7 @@ export default function SocialProofStrip({ className = '' }: SocialProofStripPro
   ].filter((card): card is { label: string; value: string } => Boolean(card));
 
   return (
-    <section className={`min-h-[260px] rounded-[2rem] border border-slate-200 bg-white p-6 shadow-sm dark:border-slate-700 dark:bg-slate-900/70 ${className}`.trim()}>
+    <section ref={sectionRef} className={`min-h-[260px] rounded-[2rem] border border-slate-200 bg-white p-6 shadow-sm dark:border-slate-700 dark:bg-slate-900/70 ${className}`.trim()}>
       <div className="flex flex-col gap-6 lg:flex-row lg:items-center lg:justify-between">
         <div className="max-w-2xl">
           <p className="text-sm font-semibold uppercase tracking-[0.2em] text-primary-600 dark:text-primary-400">