🎨 Palette: Enhance accessibility for icon-only buttons

[longestmt]

💡 What

Added aria-label attributes to icon-only buttons and aria-hidden="true" to their internal SVGs or icon characters across src/pages/workout.js, src/pages/plans.js, src/components/modal.js, and src/components/timer.js.

🎯 Why

When buttons only contain visual icons (like SVGs) and lack an explicit text label or aria-label, screen readers often announce them poorly (e.g., as "button" or by reading the SVG's inner code), making the interface difficult to navigate for visually impaired users. Adding aria-label provides a clear, descriptive action, and aria-hidden="true" prevents the screen reader from trying to read the purely visual element.

📸 Before/After

Before:
<button class="btn btn-ghost btn-icon" title="History"><svg>...</svg></button>

After:
<button class="btn btn-ghost btn-icon" title="History" aria-label="History"><svg aria-hidden="true">...</svg></button>

♿ Accessibility

This change directly improves accessibility by ensuring all interactive icon-only elements have a meaningful text alternative for assistive technologies, adhering to WCAG guidelines for non-text content.

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PR created automatically by Jules for task 13488891390287201187 started by @longestmt

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