Fix plugin check and plugin removal wording

[Snuffy2]

This pull request improves the accuracy and clarity of plugin cleanup status reporting in the OPNsense integration. The main changes ensure that log messages and user-facing descriptions more clearly indicate whether the OPNsense plugin is installed or not, and they refine the detection logic for the plugin's installation status.

Improvements to plugin installation detection:

• Updated the is_plugin_installed method in pyopnsense/__init__.py to check both the package name and that the plugin is marked as installed, preventing false positives if the package entry exists but is not actually installed.

Clarifications to log messages and user-facing descriptions:

• Updated log messages in __init__.py to explicitly state whether the OPNsense plugin is installed or not during cleanup, improving clarity for users and maintainers. [1] [2]
• Updated the English translation in translations/en.json to clarify that the plugin is not installed when cleanup is completed, making the message more informative to end users.

Partially addresses #488

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
custom_components/opnsense
__init__.py
custom_components/opnsense/pyopnsense
__init__.py
Project Total

This report was generated by python-coverage-comment-action