Redesigned chat page and story reader

A reworked chat layout, a redesigned story reader, and optional multi-message AI replies.

Chat page: layout and controls substantially reworked
Story mode: the reading view is redesigned to be clearer and more comfortable
Home screen: another round of icon arrangement, drag-and-drop and grid improvements, with better widget and icon cropping
Multiple AI replies at once: controlled by a toggle
Input and top menu: the input area and common chat shortcuts updated to match

If something looks off, hard-refresh the page first; feedback is welcome.