🎨 Palette: Add missing ARIA labels to icon-only buttons

[longestmt]

💡 What

Added missing aria-label attributes to icon-only buttons across the application (workout view, plan builder, modal, and rest timer), and added aria-hidden="true" to their inner SVG icons.

🎯 Why

In Vanilla JS apps built with template strings, icon-only buttons that rely solely on title attributes are often poorly announced or skipped by screen readers. Furthermore, inline SVGs can sometimes be read as garbled text or cause confusion if not explicitly hidden from assistive technologies. This ensures critical UI actions (delete, edit, skip timer, close modal) are fully accessible to screen reader users.

📸 Before/After

No visual changes. This is a purely structural accessibility improvement.

♿ Accessibility

• Added explicit aria-label attributes corresponding to button functions.
• Added aria-hidden="true" to SVG elements within these buttons to prevent redundant/confusing announcements.

---

PR created automatically by Jules for task 7376246487896471006 started by @longestmt

[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.