Introduces an `AnimationMode` enum with `Reactive`, `Continuous`, and
`NoAnimation` variants to allow fine-grained control over GIF playback
across the UI. This supports performance optimizations and accessibility
features, such as disabling animations when requested.
- Plumbs AnimationMode through image rendering paths
- Replaces hardcoded gif frame logic with reusable `process_gif_frame`
- Supports customizable FPS in Continuous mode
- Enables global animation opt-out via `NoteOptions::NoAnimations`
- Applies mode-specific logic in profile pictures, posts, media carousels, and viewer
Animation behavior by context
-----------------------------
- Profile pictures: Reactive (render only on interaction/activity)
- PostView: NoAnimation if disabled in NoteOptions, else Continuous (uncapped)
- Media carousels: NoAnimation or Continuous (capped at 24fps)
- Viewer/gallery: Always Continuous (full animation)
In the future, we can customize these by power settings.
Signed-off-by: William Casarin <jb55@jb55.com>