a11y: Several image elements are missing alt text

Summary Multiple <img> elements across the studio render without an alt attribute, so screen readers can't describe them and the markup fails basic accessibility/lint checks.

Where (non-exhaustive)

• apps/studio/src/app/layout/main-layout.tsx:140
• apps/studio/src/features/studio/components/file-list-panel.tsx:162
• apps/studio/src/features/studio/components/canvas/canvas.tsx:54
• apps/studio/src/features/projects/components/image-upload.tsx:64
• apps/studio/src/features/projects/components/image-table.tsx:95
• apps/studio/src/features/studio/components/editors/video/video-library.tsx:180

Find the rest with: grep -rn "<img" --include=*.tsx apps/studio/src | grep -v "alt="

Steps

1. Branch: git checkout -b a11y/img-alt-text.
2. Add a descriptive alt to each (e.g. alt={image.name} for dataset thumbnails, alt="Vailabel logo" for the logo). Use alt="" only for purely decorative images.
3. Run yarn lint and yarn typecheck; open a PR.

Acceptance criteria

• Every meaningful <img> has a descriptive alt; decorative ones use alt="".
• grep -rn "<img" --include=*.tsx apps/studio/src | grep -v "alt=" returns nothing.

Good first issue — comment here if you'd like to take it.