Fix Firefox table scrollbar visibility

[subhajitlucky]

Fixes #8

Summary

• Fix Firefox scrollbar styling in the shared table component.
• Use Firefox-compatible scrollbar-color with both thumb and track colors.
• Add scrollbar-gutter: stable so scrollable panels reserve consistent scrollbar space.

Verification

• npm run build
• git diff --check

Note: build passes with the repository's existing Svelte/Rollup warnings.

[Copilot]

Pull request overview

Updates the shared Table component’s CSS to improve scrollbar appearance/behavior in Firefox, addressing issue #8 (“Panel scrollbars do not appear on Firefox”) by using Firefox-valid scrollbar-color syntax and reserving scrollbar space to reduce layout shifting.

Changes:

• Fix Firefox scrollbar styling by specifying both thumb and track colors via scrollbar-color: <thumb> <track>.
• Add scrollbar-gutter: stable on the horizontal (.table-wrapper, mobile) and vertical (.data-wrapper) scroll containers to reserve consistent scrollbar space.

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