GUI: Fix restricted asset clear slots

[Tabakkui]

Problem

Issue #968 reports Qt connection warnings when opening Restricted Assets:

• No such slot AssignQualifier::clear()
• No such slot FreezeAddress::clear()

Both widgets connect their buttonClear signals using the string-based Qt SLOT(clear()) syntax, but clear() was declared as a regular public method rather than a meta-object slot.

Change

Declare AssignQualifier::clear() and FreezeAddress::clear() in public Q_SLOTS. The existing connections and clear implementations remain unchanged.

Test plan

• git diff --check
• Verified both headers place void clear(); directly under public Q_SLOTS:.
• Confirmed the existing buttonClear connections use SLOT(clear()).

The checkout is unconfigured and Qt's moc executable is not installed on this ARM64 host, so no generated-meta-object or full Qt build was run. The authorized PC should run the Qt build/test gate.

Fixes #968