Add licensing acknowledgment dialog on startup and update About dialog

[HammerGS]

Note: Depends on MegaMek PR (uses LicensingDialog from megamek) MegaMek/megamek#8164

Summary

Integrates the MegaMek Suite licensing dialog into MegaMekLab startup and updates the About dialog to use aligned legal text with clickable links.

Changes

1. MegaMekLab.java - Added LicensingDialog.showIfNeeded() call in startup() after GUI scaling, showing "Welcome to
   MegaMekLab [VERSION]".
2. MenuBar.java - Updated aboutAction() to use aligned legal text from MegaMek's LicensingDialog.* message keys via
   Messages.getString(), replacing outdated GPL-only text.

Files Changed

• megameklab/src/megameklab/MegaMekLab.java
• megameklab/src/megameklab/ui/MenuBar.java

[Copilot]

Pull request overview

Integrates MegaMek Suite’s licensing acknowledgment flow into MegaMekLab by showing the shared licensing dialog on startup and aligning MegaMekLab’s About dialog legal text with MegaMek’s message keys (including clickable links).

Changes:

• Show LicensingDialog.showIfNeeded() during MegaMekLab startup with a “Welcome to MegaMekLab [VERSION]” message.
• Update the About dialog to render HTML assembled from MegaMek’s LicensingDialog.* / CommonAboutDialog.* i18n keys and enable hyperlink navigation.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
megameklab/src/megameklab/MegaMekLab.java	Adds licensing/welcome dialog invocation during startup.
megameklab/src/megameklab/ui/MenuBar.java	Reworks About dialog body to use MegaMek legal/community text keys and clickable links.

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[HammerGS]

Copilot feedback addressed in commit 65da303:

1. --no-startup guard — LicensingDialog.showIfNeeded() is now guarded with if (!noStartup) so it won't pop a GUI dialog during batch .mul processing.

2. Dialog timing — Moved the dialog call to after the startup screen is displayed, so both appear together instead of the dialog blocking before the main window.

Additional fixes:

• Uses MMLConstants.PROJECT_NAME constant instead of hardcoded string
• Replaced Desktop.getDesktop().browse() with UIUtil.browse() in MenuBar for platform-safe hyperlink handling
• Replaced duplicate buildAboutHtml() with shared LicensingDialog.buildLegalHtml() from the megamek PR