Build 275: Read Aloud on the Lock Screen, and a Library that opens smoothly

[briarrrn]

Read Aloud now behaves like a proper audio app. It keeps playing when the screen locks, and the Lock Screen shows a real card: the book's cover, title and author, with play/pause that works. The skip arrows say 15 seconds but each tap moves one paragraph, which is about the same distance in prose. Locking mid-listen no longer resets your reading position, and a crash that could hit right when that card appeared is fixed.

The Library's stuttery scrolling finally got a proper diagnosis. Covers now come straight from the cache instead of asking the server about each one, they decode at the size the grid actually shows, and the background sync waits while you scroll instead of catching the animation every second. Opening the Library after a fresh start should be smooth from the first second.

If scrolling still catches on your device, please tell me what you see and roughly how big your library is.

Fixes reported here: #75