Fix QGIS plugin reload cleanup

[giswqs]

Summary

Fix QGIS Plugin Reloader warnings caused by custom plugin toolbars and menus that can remain attached to the QGIS main window after unload().

Changes

• Remove stale plugin toolbars by object name before creating a new toolbar.
• Detach and schedule stale toolbars for deletion during unload.
• Remove stale plugin menus by title before initialization and during unload.
• Keep cleanup best-effort so reload/unload can continue even if QGIS has already detached a widget.

Validation

• Ran python -m py_compile on the changed plugin entry-point file.
• Ran git diff --check.

[github-actions]

🚀 Deployed on https://6a02ab80157e69a3cc3b518b--opengeos.netlify.app

[Copilot]

Pull request overview

This PR aims to reduce QGIS Plugin Reloader warnings by proactively cleaning up SamGeo plugin UI elements (toolbars/menus) that may persist after unload() during reload cycles.

Changes:

• Added best-effort cleanup utilities to detach and schedule deletion of stale toolbars/menus.
• Removed stale toolbars by object name before creating a new toolbar and again during unload().
• Attempted to remove stale plugin menus by title during initialization and unload().

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