Restore transition style + speed at global, app, and playlist levels

[csader]

Background

Adam's original UI had per-page style (module send order: ltr, rtl, diagonal, spiral, etc.) and speed (ms between module commands) controls on every playlist page. These were removed when the compose tab was simplified. The backend already supports both fields on page objects — they just aren't exposed in the UI.

What to restore

Level 1: Global default

• New settings: transition_style (default: ltr) and transition_speed (default: 15ms)
• Shown in Settings under the Display section alongside the existing Transition Effect controls
• Used as fallback when no per-app or per-page override is set

Level 2: Per-app override

• Apps can declare transition_style and transition_speed in their manifest settings
• Shows up in the app settings modal like any other setting
• _send_with_effect() checks for a per-app override before falling back to global

Level 3: Per-page override

• App playlist compose entries — style + speed controls in the compose entry row alongside the existing delay input
• Compose tab — style dropdown and speed input below the grid editor; sync() reads these when pushing to display

Note

"Transition style/speed" is distinct from the new flap effects (wave/sync/slot). Style/speed control which order modules fire and how fast commands are sent. Effects control timing coordination between modules. When a flap effect is active, it overrides style/speed.

[csader]

Implemented in feat/transition-style-speed.