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

dotfiles/desktop/.config/waybar/style.css

@@ -0,0 +1,90 @@
+* {
+  border: none;
+  border-radius: 0;
+  min-height: 0;
+  padding: 0;
+  margin: 0;
+  font-family: "Liberation Mono", monospace;
+  font-size: 12px;
+}
+
+window#waybar {
+  background: #1f1f28;
+  color: #d0d0d0;
+  border-top: 2px solid #3a3a46;
+}
+
+#workspaces,
+#pulseaudio,
+#backlight,
+#network,
+#bluetooth,
+#battery,
+#temperature,
+#memory,
+#clock,
+#custom-powermenu,
+#tray {
+  padding: 0 8px;
+  margin: 3px 0;
+}
+
+#workspaces {
+  padding-left: 10px;
+}
+
+#workspaces button {
+  background: transparent;
+  color: #9a9a9a;
+  padding: 0 7px;
+  margin: 0 2px;
+  border-top: 2px solid transparent;
+}
+
+#workspaces button:hover {
+  color: #d0d0d0;
+  background: transparent;
+}
+
+#workspaces button.active {
+  color: #ffffff;
+  border-top: 2px solid #4a90d9;
+}
+
+#workspaces button.urgent {
+  color: #ffffff;
+  background: #c7162b;
+}
+
+#pulseaudio,
+#backlight,
+#network,
+#bluetooth,
+#battery,
+#temperature,
+#memory {
+  color: #d0d0d0;
+}
+
+#clock,
+#custom-powermenu {
+  color: #ffffff;
+}
+
+#clock {
+  padding: 0 12px;
+}
+
+#custom-powermenu {
+  padding: 0 12px;
+}
+
+#tray {
+  padding-right: 12px;
+}
+
+tooltip {
+  background: #1f1f28;
+  border: 1px solid #4a90d9;
+  color: #d0d0d0;
+}