Replace Rofi with Walker as application launcher

Walker (GTK4 + Elephant backend) replaces rofi-lbonn-wayland-git as the
central launcher and menu framework.

Native Walker providers replace 5 custom rofi scripts:
- App launcher (desktopapplications provider)
- Clipboard (clipboard provider, replaces cliphist frontend)
- Bluetooth (bluetooth provider, replaces bluetoothctl script)
- Volume/audio (wireplumber provider)
- Sink switcher (wireplumber provider)

3 scripts ported to Walker dmenu mode:
- moonarch-vpn (nmcli)
- moonarch-cpugov (auto-cpufreq)
- moonarch-sink-switcher (pactl)

Settings menu (moonarch-setmen) removed — apps are findable via Walker
app search directly.

Walker theme (gtk-inherit) inherits all colors from the active GTK4
theme instead of hardcoding Catppuccin values.

Walker and Elephant run as systemd user services for instant startup.

Also standardizes GTK theme to Colloid-Grey-Dark-Catppuccin across all
config files (was inconsistent between gsettings and file configs).

Old rofi configs preserved in legacy/rofi/ for reference.

legacy/rofi/bin/moonarch-clipboard

@@ -0,0 +1,26 @@
+#!/usr/bin/env bash
+# ABOUTME: Rofi-based clipboard history manager using cliphist and wl-copy.
+# ABOUTME: Lists clipboard entries and copies the selected one.
+
+CLIPHIST_DB="${XDG_RUNTIME_DIR:-/run/user/$(id -u)}/cliphist/db"
+
+function start_rofi() {
+    local content="$1"
+    echo -e "$content" | rofi -dmenu -theme /etc/xdg/rofi/themes/clipboard.rasi -mesg "󰅍  Clipboard History"
+}
+
+function main() {
+    local entries
+    local result
+
+    entries=$(cliphist -db-path "$CLIPHIST_DB" list)
+    result=$(start_rofi "$entries")
+
+    if [ -n "$result" ]; then
+        echo "$result" | cliphist -db-path "$CLIPHIST_DB" decode | wl-copy
+    else
+        exit 1
+    fi
+}
+
+main