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/templates/emptty-conf.j2

@@ -0,0 +1,18 @@
+TTY_NUMBER=7
+SWITCH_TTY=true
+DEFAULT_ENV={{ desktop_default_session_env | default('xorg') }}
+{% if not (desktop_prompt_for_session | default(false)) and (desktop_default_session | default('')) | length > 0 %}
+DEFAULT_SESSION={{ desktop_default_session | default('') }}
+{% if (desktop_default_session_env | default('')) | length > 0 %}
+DEFAULT_SESSION_ENV={{ desktop_default_session_env | default('') }}
+{% endif %}
+{% endif %}
+DBUS_LAUNCH=false
+XINITRC_LAUNCH=true
+XORG_SESSIONS_PATH=/etc/emptty/xsessions
+WAYLAND_SESSIONS_PATH=/etc/emptty/wayland-sessions
+VERTICAL_SELECTION=true
+IDENTIFY_ENVS=true
+SELECT_LAST_USER=global
+LOGGING=rotate
+SESSION_ERROR_LOGGING={{ desktop_emptty_session_error_logging | default('disabled') }}