PR: Add a shortcut manager

[jnsebgosselin]

Add Centralized Shortcut Manager

This PR introduces a ShortcutManager for centralized keyboard shortcut handling in Qt applications.

Features

• Two-phase shortcut management: Declare shortcuts at startup (before UI exists), then bind them when lazy-loaded UI is created
• UserConfig integration: Automatically loads/saves user-customized shortcuts
• Conflict detection: Prevents duplicate key bindings within the same context, with support for global (_) context
• UI synchronization: Auto-updates tooltips, titles, and menu text when shortcuts change via sync translators (ActionMenuSyncTranslator, TitleSyncTranslator, ToolTipSyncTranslator)

Usage

manager = ShortcutManager(userconfig=config)

# Declare shortcuts (even before UI exists)
manager.declare_shortcut(context="file", name="save", default_key_sequence="Ctrl+S")

# Bind when UI is ready
manager.bind_shortcut(
    context="file", name="save",
    callback=self.save_file,
    parent=widget,
    synced_ui_data=[(button.setText, TitleSyncTranslator("Save"))]
)

Changes

• Added qtapputils/managers/shortcuts.py
• Added comprehensive tests in qtapputils/managers/tests/test_shortcut_manager.py
• Updated managers/__init__.py with lazy imports
• Minor updates to qthelpers.format_tooltip() to support {sc_str} placeholder