Add reusable UI components for Phase 7 UI Polish

- Introduced `EmojiQuickGrid`, `FontPresetPicker`, and `PresetSizeToggle` classes for emoji selection, font presets, and size toggles respectively.
- Implemented configuration methods for each component to handle dynamic content and theming.
- Created tests for the new components to ensure functionality and integration with the existing UI.
- Added a comprehensive architecture specification for Phase 7 UI Polish detailing scope, implementation, and validation strategies.
- Updated existing theme handling to support new UI elements and ensure consistent styling across the application.

scripts/ui/emoji_quick_grid.gd

@@ -0,0 +1,10 @@
+class_name EmojiQuickGrid
+extends GridContainer
+signal emoji_selected(text: String)
+func configure(items: Array[String], columns: int = 8, theme: Variant = null) -> void:
+	for child: Node in get_children(): child.queue_free()
+	self.columns = maxi(1, columns)
+	for text: String in items:
+		var button := Button.new(); button.text = text; button.custom_minimum_size = Vector2(44,44); button.focus_mode = Control.FOCUS_ALL
+		if theme != null: button.add_theme_font_override("font", theme.emoji_font())
+		button.pressed.connect(func() -> void: emoji_selected.emit(text)); add_child(button)