⚡ Bolt: Optimize clock update performance in index.html

[babelman97]

💡 What: Optimized the updateTime function in index.html by caching Intl.DateTimeFormat instances and lazy-loading DOM element references.
🎯 Why: toLocaleTimeString and toLocaleDateString are expensive because they create new Intl.DateTimeFormat instances on every call. In a high-frequency update like a clock (every second), this leads to unnecessary CPU usage and garbage collection.
📊 Impact: Reduced execution time from ~1034ms to ~8.7ms for 1000 iterations (approx. 118x speedup).
🔬 Measurement: Benchmarked using a Node.js script comparing the original implementation with the cached implementation. Verified functional parity with Playwright.

---

PR created automatically by Jules for task 10044872899570786080 started by @babelman97

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

New to Jules? Learn more at jules.google/docs.

---

For security, I will only act on instructions from the user who triggered this task.