UI/UX: RTL preparation and virtualized ledger table

[DeborahOlaboye]

Summary

This PR addresses 2 issues with 2 commits:

Commit 1: design: RTL preparation across layout and icons (Closes #155)

• Replaced physical CSS properties with logical equivalents across index.css, AppShell.css, StatusTimeline.css, KeyboardShortcutsOverlay.css, and DesignTokensPage.css
• Added [dir="rtl"] CSS overrides for directional components (mobile drawer, timeline, tooltips)
• Added .icon-rtl utility class for icons that mirror in RTL (ArrowLeft, ChevronRight)
• Added RTL-aware positioning and spacing utility overrides
• Fixed inline marginRight style in StatusTimeline.tsx to use marginInlineEnd
• Added RTL variant of the shake animation

Commit 2: design: virtualized ledger table with column controls (Closes #139)

• New LedgerTable component with virtualized row rendering
• Sticky header with proper ARIA role="grid" semantics
• Column visibility menu with toggle controls and minimum-1-column protection
• Density toggle (compact/normal/spacious)
• Row-detail side drawer with expand/collapse
• Pagination for large datasets
• Keyboard navigation (ArrowUp/ArrowDown/Enter/Escape)
• Full test coverage (11 tests passing)
• Demo page at /investor/ledger

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