Add nextcloud-client and blueman: the two tray apps get an owner and tools, each with one start

Both are official packages already on both workstations, started once by dex from an XDG
autostart entry (the client's own, the package's). The modules declare the package, add no
second start, own none of the apps' files, and give the mesh status, log, restart and check.

modules/bluetooth/README.md

@@ -48,6 +48,6 @@ running. `bluez` becomes explicitly the mesh's.
 ## Leaves as found
 
 - The paired devices and their keys under `/var/lib/bluetooth` (bluez's state).
-- `blueman` on both workstations, and its applet, which the window manager's configuration starts.
-  That line is the `i3` module's to keep or drop.
+- `blueman` and its applet: the `blueman` module's, which relies on this one for the stack and
+  declares none of its packages. The applet starts from the package's XDG autostart entry.
 - `bluez-obex` and the AUR terminal client `bluetuith-bin` (with its `-debug`) on the laptop.