⚡ Email Queue Table Check Optimization

[irgordon]

💡 What: Optimized EmailService::tableExists and EmailService::adminQueueTableExists to use a persistent transient cache (24 hours).
🎯 Why: These methods perform SHOW TABLES LIKE ... queries which can be redundant and slow, especially during high-volume queue operations. Caching the result eliminates this database overhead for the vast majority of requests.
📊 Measured Improvement: Validated with tests/benchmark_email_service_table_exists.php:

• Before: ~0.51s for 50 iterations (simulated 10ms latency).
• After: ~0.01s for 50 iterations.
• Speedup: ~50x speedup for repeated checks.
• Overhead: Reduced from ~10ms per call to ~0.2ms per call.

---

PR created automatically by Jules for task 7054742044208042653 started by @irgordon

[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.