linux-visualizator: add new desklet

[KoDiK2005]

Summary

New desklet: real-time visualization of CPU (per-core rings/bars/graph), RAM/Swap,
network traffic, disk usage/I/O, and GPU load/memory/temperature.

• GPU support for NVIDIA (via nvidia-smi) and AMD (via amdgpu sysfs); the section
  is omitted automatically if no supported GPU is detected.
• Per-category accent colors, adjustable warning/critical color thresholds, an
  interface scale slider, configurable section order, and disk/network filters.
• Click-to-launch a configurable command (defaults to gnome-system-monitor).
• All /proc reads and subprocess calls use asynchronous GIO APIs
  (load_contents_async, communicate_utf8_async, enumerate_children_async).
• UI strings are in English, wrapped with Gettext.dgettext for future translation.

Source repo (also has an independent Python/Qt implementation of the same idea):
https://github.com/KoDiK2005/linux-visualizator

Test plan

• ./validate-spice linux-visualizator@KoDiK2005 passes with no errors
• node --check desklet.js passes
• Installed and tested live on Linux Mint 22.3 (Cinnamon) via cinnamon --replace;
  confirmed no JS errors in the log and correct rendering of all sections

[github-actions]

Best-practices scanner

This is a regex-based check for API usage that can pose security, performance or
maintainability issues, or that may already be provided by Cinnamon. Most findings
are advisory and do not automatically disqualify a pull request.

This check is not perfect and will not replace a normal review.

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Found 4 potential issue(s):

⚠️ WARNING

⚠️ hardcoded_data_dir

linux-visualizator@KoDiK2005/files/linux-visualizator@KoDiK2005/desklet.js:13

Gettext.bindtextdomain(UUID, GLib.get_home_dir() + '/.local/share/locale');

Avoid hardcoding .local/share in paths. Use GLib.get_user_data_dir() instead,
which respects the XDG_DATA_HOME environment variable.

⚠️ lang_bind

linux-visualizator@KoDiK2005/files/linux-visualizator@KoDiK2005/desklet.js:598

this._timeoutId = Mainloop.timeout_add(intervalMs, Lang.bind(this, this._tick));

Lang.bind() is deprecated. Use arrow functions (() => {}) or Function.prototype.bind() instead.

linux-visualizator@KoDiK2005/files/linux-visualizator@KoDiK2005/desklet.js:605

this._animationTimeoutId = Mainloop.timeout_add(ANIMATION_INTERVAL_MS, Lang.bind(this, this._animateStep));

Lang.bind() is deprecated. Use arrow functions (() => {}) or Function.prototype.bind() instead.

ℹ️ INFO

ℹ️ shell_string_spawn

linux-visualizator@KoDiK2005/files/linux-visualizator@KoDiK2005/desklet.js:512

GLib.spawn_command_line_async(command);

Prefer argument vector spawn functions over shell command strings.
This is especially important when arguments include untrusted input (user data,
filenames, settings values, etc.) as shell strings are vulnerable to injection.
Static command strings are generally fine, but argv is always safer.
Use Util.spawn(["cmd", "arg1", "arg2"]) or Util.trySpawn() instead.

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Automated pattern check.

[claudiux]

Please take into account the "Best practices" above.