Reorganize desktop roles: extract common bootstrap and host-specific layers

- Add profile_desktop_common with shared desktop bootstrap (emptty, PAM,
  dotfiles, templates, GPG, Maildir, Flatpak, st, external tools)
- Add profile_desktop_host with host-specific tasks (NVIDIA/PRIME on nymph)
- Reduce profile_desktop_i3 to i3/X11-only tasks
- Create profile_desktop_hyprland for Hyprland Wayland session
- Add dual-session support (i3 + Hyprland) on nymph with session choice
- Create shared Hyprland/Waybar dotfiles under dotfiles/desktop/
- Fix Waybar: bottom position, no persistent workspaces, sort by number
- Rename host_dotfiles to host_i3_dotfiles for clarity
- Make emptty restart manual by default to avoid session drops

ansible/roles/profile_desktop_common/handlers/main.yml

@@ -0,0 +1,19 @@
+---
+- name: Restart emptty service
+  listen: Restart emptty
+  ansible.builtin.command: sv restart emptty
+  changed_when: true
+  when:
+    - not ansible_check_mode
+    - desktop_restart_emptty_automatically | default(false)
+
+- name: Report manual emptty restart requirement
+  listen: Restart emptty
+  ansible.builtin.debug:
+    msg: >-
+      Emptty configuration changed but automatic restart is disabled.
+      Restart it manually from SSH or another TTY with `sudo sv restart emptty`
+      to avoid dropping the active graphical session.
+  when:
+    - not ansible_check_mode
+    - not (desktop_restart_emptty_automatically | default(false))