and other cleanup

+ reorganize tray menu items

+ expand unit labelks
+ improve IntervalCard spacing

+ font application across ui

- replace display_info with native wl_output enumeration; detects
connected outputs more reliably
- create one slint window per monitor
- use winit_window().await + fullscreen::borderless()monitorhandle) to
call xdg_toplevel.setfullscreen(wl_output)
- fix dead-code warnings

"wlr-layer-shell barrier for secondary Wayland monitors

Adds `src/overlay/layer_shell.rs` with `LayerShellBarrier`: connects to
Wayland, probes for `zwlr_layer_shell_v1`, and on Show creates opaque
layer surfaces (Overlay layer, all-anchored, exclusive-zone -1) on every
non-primary output using a dedicated background thread. Primary output
is intentionally skipped because the Slint window covers it.
`OverlayManager` now owns an optional `LayerShellBarrier` on
Linux/Wayland and calls `show`/`hide` alongside the existing Slint
backend."

- set explicit window height
- remove ScrollView

- eliminate RefCell double-borrow crash
- show() before set_fullscreen()
- reset snooze_used per break
- center progres bar in overlay
- lazy overlay creation