⚡ Bolt: optimize dashboard clock and time zones

[babelman97]

💡 What: Optimized the dashboard clock and time zone display in index.html.

🎯 Why: The original implementation repeatedly called toLocaleTimeString and toLocaleDateString (which are expensive because they instantiate Intl objects) and used innerHTML to rebuild entire DOM subtrees every second, leading to unnecessary layout and parsing overhead.

📊 Impact:

• Execution Speed: Reduced updateTime execution duration from ~1.83ms to ~0.017ms per call (approx. 100x faster).
• DOM Efficiency: Replaced full container re-renders with targeted textContent updates.
• Resource Usage: Caches formatters and DOM references, and skips date updates when unchanged (dirty-checking).

🔬 Measurement: Verified using a Playwright-based benchmark script calling updateTime 1000 times in a loop. Visual parity confirmed via Playwright screenshots.

---

PR created automatically by Jules for task 17791100830354043568 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.