[shelly](fix): support shelly v3

[joshuaslate]

Plugin

• Id: joshuaslate/shelly
• New plugin
• Update to an existing plugin (version bumped in plugin.toml)

What it does

A new major of Shelly was released (v3), which broke this plugin (see #181). This fixes the issues there and adds the requested features:

• Ability to show just the count in the widget (e.g., "5" instead of "5 Updates")
• Ability to change font size in the widget

External dependencies

Testing

Waited for package updates, saw the count increase, saw the updates available in the tooltip, then clicked through to upgrade all dependencies.

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Noctalia version tested against: noctalia v5.0.0 (v5.0.0-beta.7-8-ga7d2cad44217)
• Plugin API level: 3

Screenshots / Videos

I didn't grab a screenshot before updating... but the count was > 0, and it showed properly.

Checklist

• The directory name matches the part of id after the / in plugin.toml exactly.
• It ships plugin.toml, README.md, thumbnail.webp, and translations/en.json.
• README.md follows the
  README template, documents
  every entry id and dependency, and includes exact panel IPC commands and launcher prefixes where applicable.
• I created thumbnail.webp with the thumbnail generator.
• version follows semver and is bumped in this PR; plugin_api is the oldest API level this plugin requires.
• Every non-English translation in this PR uses a locale supported by Noctalia core, and I can read, write, and
  understand that language well enough to review and maintain it (no unreviewed machine/LLM translations).
• I did not edit catalog.toml; CI generates it.
• This PR touches exactly one plugin directory.

Code review attestation

Plugins run as trusted, unsandboxed Luau in the user's session. Confirm:

• The code is readable and not obfuscated, minified, or generated.
• It does not download and execute remote code. ** Not without explicit user interaction. The whole point of this plugin is to update dependencies via Shelly. This plugin only opens shelly and the user handles downloading & updating their packages from there. **
• Every network call, filesystem write, and spawned process is something the description above accounts for.
• I have the right to publish this code under the license declared in plugin.toml.