Refactor ApexAIPage into modular components with chat-first layout

[Copilot]

ApexAIPage.jsx was a ~325-line monolith mixing hero content, sidebar panels, chat UI, and inline styles. The chat interface was pushed far below the fold, burying the core product interaction behind decorative content.

Component extraction (components/apexai/)

Component	Responsibility
HeroSection	Badge, title, tagline, stats — pure display
FeatureGrid	4 capability cards — moved below the fold
MessageBubble	Single message with user/assistant styling
LoadingIndicator	Animated typing dots
ChatInput	Input + send form
ChatWindow	Composes header + messages + input
BottomCTA	Black CTA strip

ApexAIPage.jsx is now an ~80-line state orchestrator:

<section className="flex-1 flex flex-col lg:flex-row border-b-4 border-black min-h-[600px]">
  <div className="lg:w-[360px] xl:w-[400px] ... flex flex-col p-6 sm:p-8">
    <HeroSection />
  </div>
  <div className="flex-1 flex flex-col min-h-[500px] lg:min-h-0">
    <ChatWindow messages={messages} isLoading={isLoading} ... />
  </div>
</section>

Layout & UX changes

• Chat-first: Desktop shows a split viewport — compact hero sidebar (360px) + chat filling remaining width/height. Chat is visible without scrolling.
• Removed: Quick Commands panel and Session Stats sidebar.
• Status indicator: Green/yellow dot in chat header reflects Ready/Analyzing state.
• Mobile: Hero stacks above chat (min-h-[500px] guard on chat window).
• FeatureGrid + BottomCTA remain accessible below the fold.

Technical cleanup

• Removed non-functional <style jsx> block (Styled JSX is Next.js only; had no effect in Vite). Scrollbar styles moved to index.css as .apex-scrollbar.
• Dropped unused messagesEndRef, quickPrompts, and handleQuickPrompt.
• handleSendMessage de-async'd; marked with TODO for real API wiring.