feat: implement undo/redo functionality in video editor

[FabLrc]

Pull Request : implement undo/redo functionality in video editor

Description

Adds a full undo/redo system to the video editor, backed by a custom useEditorHistory hook using a snapshot history pattern. Includes keyboard shortcuts and a slider commit support.

Motivation

The editor had no way to revert accidental changes (deleted zoom region, wrong crop, slider overshoot, etc.). Users needed standard undo/redo behaviour without introducing a heavy state management library.

Type of Change

• New Feature
• Bug Fix
• Refactor / Code Cleanup

Related Issue(s)

#170

Screenshot

Changes

New: src/hooks/useEditorHistory.ts

• Custom hook encapsulating a past/present/future snapshot stack (max 80 entries)
• Three operations:
  • pushState — discrete undo point (region add/delete, aspect ratio change, etc.)
  • updateState — live preview during drag/slider interaction; auto-saves a checkpoint on first call via a dirtyRef
  • commitState — resets the dirty flag when the interaction ends (pointer-up, slider commit)
• Pure helper functions resolve() and withCheckpoint() keep the hook stateless and testable

Modified: VideoEditor.tsx

• Replaced ~15 individual useState hooks for undoable fields with a single useEditorHistory call
• All region mutations (pushState), slider interactions (updateState / commitState), and zoom focus drags wired accordingly
• Global keyboard handler (capture phase) handles Ctrl+Z (undo), Ctrl+Shift+Z and Ctrl+Y (redo); uses e.key.toLowerCase() to handle the uppercase 'Z' returned by browsers when Shift is held

Modified: VideoPlayback.tsx

• Added onZoomFocusDragEnd?: () => void prop, called on pointer-up/leave, so dragging the zoom focus point creates a single undo entry instead of one per frame

Modified: timeline/TimelineEditor.tsx

• Single-letter shortcuts (Z, T, A, F) guarded with !e.ctrlKey && !e.metaKey && !e.altKey to prevent conflict with Ctrl+Z

Modified: SettingsPanel.tsx

• Added onShadowCommit, onBorderRadiusCommit, onPaddingCommit props wired to Radix Slider's onValueCommit, completing the updateState/commitState pattern for all sliders

Modified: KeyboardShortcutsHelp.tsx

• Added Undo (Ctrl+Z) and Redo (Ctrl+Shift+Z / Ctrl+Y) rows to the shortcuts tooltip

Testing

Tested on Windows

Checklist

• I have performed a self-review of my code.
• I have added any necessary screenshots or videos.
• I have linked related issue(s) and updated the changelog if applicable.

[shivaylamba]

this comment seems incomplete

[shivaylamba]

looks good

[siddharthvaddem]

LGTM, can you make sure to rebase this on top of main? I added linter checks, so the PR will fail these checks until you fix them. I would like this in for the next release.