More controls for media in lightbox

[Darkkal]

Overview

Enhance the lightbox with better media controls: full-height navigation zones, fit mode selection, zoom/pan capabilities, show/hide controls with auto-hide, and pinch-to-zoom on mobile. All new preferences are configurable in the existing /settings page.

Key Design Decisions

Fit Mode vs Zoom (Mutually Exclusive)

Two independent display modes for media:

• Fit Mode: How media is sized to the container. Options: Fit Both (default, current object-fit: contain), Fit Width, Fit Height.
• Zoom Mode: Raw scale percentage (e.g. 50%, 100%, 200%) within configurable min/max bounds. When zoomed, media is pannable.

Key rule: If fitting, the zoom level is not used. If zooming, the fitting behavior is not used.

Controls Visibility

• Manual toggle via button, image click, or H key
• Auto-hide after configurable inactivity delay
• Master toggle: hiding controls also hides sidebar; showing restores prior state
• Two-step Escape: first press shows controls, second closes lightbox

Navigation Zones

• Full-height click zones on left/right edges, separate from media
• Fixed position regardless of media dimensions
• Subtle hover reveal with gradient + chevron

Resolved Decisions

Decision	Resolution
Fit mode selector UI	Icon button that cycles through modes (no dropdown)
Zoom level indicator	Small transient numeric overlay (e.g., "150%") that fades after ~1.5s
Scroll wheel direction	Scroll-up = zoom in (standard convention, not configurable)
Pinch-to-zoom	Sub-Issue 5, shares zoom bounds from settings

Recommended Implementation Order

1. Lightbox Settings — Adds the AppSettings fields that all other sub-issues depend on
2. Full-Height Nav Zones — Simple structural change, establishes controls that show/hide will manage
3. Show/Hide + Auto-Hide — Builds the controlsVisible framework that zoom buttons plug into
4. Fit Mode & Zoom — Most complex feature, relies on settings, nav zones, and controls framework
5. Pinch-to-Zoom — Mobile gesture layer on top of the zoom infrastructure