🎨 Palette: Accessibility Hardening for Overlay Controls

[soulllink]

💡 What: Added aria-label attributes to icon-only buttons, inputs, and sliders in OverlayControls.svelte. Added role="status" to the loading spinner.
🎯 Why: To make the application's primary controls accessible to screen reader users and comply with accessibility standards. Previously, these controls were announced only as "button" or by their file names, making them unusable for non-sighted users.
♿ Accessibility:

• Added accessible names for: Open Folder, View Modes (1:1, Fit, Reader, Landscape), OCR Toggle, Settings, Hide/Show UI, Go To input/button.
• Added accessible names for all 6 image adjustment sliders (Brightness, Contrast, etc.).
• Added status role to loading indicator.

---

PR created automatically by Jules for task 10274009942531255908 started by @soulllink

[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.