feat: scaffold conky_widget desktop monitor

Conky (X11 + Lua + Cairo) desktop widget with three clickable tabs
(Red / Sistema / Docker) rendered entirely with Cairo:

- Red: live down/up speed for enp5s0, 60s history graph, active
  connections count, totals, and launcher buttons for Wireshark,
  ntopng and nethogs (with notify-send fallback when missing).
- Sistema: total CPU + per-core bars, RAM, swap, root disk usage,
  temperature, load average and uptime.
- Docker: running/total container count and active container names
  (read without sudo).

Includes install.sh (symlink into ~/.config/conky + XFCE autostart),
launch.sh (tool launcher with missing-binary fallback) and app.md
with e2e_checks. Positioned top-right of the primary monitor
(xinerama_head 0), configurable.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lua/launch.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+# Lanza una herramienta si su binario existe; si falta, avisa con notify-send
+# indicando el paquete a instalar. Llamado desde widget.lua al clicar un boton.
+#
+# Uso: launch.sh <binario_a_comprobar> <paquete-apt> <comando-shell>
+set -u
+
+bin="${1:-}"
+pkg="${2:-}"
+cmd="${3:-}"
+
+if [ -z "$bin" ] || [ -z "$cmd" ]; then
+    exit 1
+fi
+
+if command -v "$bin" >/dev/null 2>&1; then
+    setsid sh -c "$cmd" >/dev/null 2>&1 &
+else
+    notify-send "conky_widget — falta herramienta" \
+        "No esta '$bin'. Instalar:  sudo apt install $pkg" 2>/dev/null || true
+fi