Move the filter bar and the timeline onto the library's Slint global

The date-range fields and their band on the capture-time axis, the
timeline's bars, labels, scrub/pinch/pan/zoom callbacks and its
sweep/current-bucket/anchored state, and the filter bar's people chips,
mode, eyes-open toggle and gesture reference move from AppWindow onto the
`Library` global. Rust reaches them through window.global::<Library>()
rather than window.set_/get_/on_ on the root, as the earlier commits on
this branch did for the grid's cells, selection, ratings and keywords.

ui/dr-ui/src/library_ui/open.rs

@@ -85,7 +85,9 @@ pub fn open(
     window.set_library_status("Starting…".into());
     // Always visible: two folders one letter apart are easy to confuse, and a
     // scan of the wrong one is indistinguishable from a broken scan.
-    window.set_library_root_label(library_root_label(&conn.account).into());
+    window
+        .global::<Library>()
+        .set_library_root_label(library_root_label(&conn.account).into());
 
     // An empty filter would walk the whole tree and match nothing, which looks
     // exactly like a broken scan. Say so instead.