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/preset_size_toggle.gd

@@ -0,0 +1,25 @@
+class_name PresetSizeToggle
+extends HBoxContainer
+signal preset_selected(id: String, value: int)
+var _presets: Array[Dictionary] = []
+var _selected_id: String = ""
+var _group: ButtonGroup = ButtonGroup.new()
+func configure(presets: Array[Dictionary], selected_id: String, theme: Variant = null) -> void:
+	for child: Node in get_children(): child.queue_free()
+	_presets = presets.duplicate(true); _selected_id = selected_id
+	for item: Dictionary in _presets:
+		if String(item.get("id","")).is_empty(): continue
+		var button := Button.new(); button.text = String(item.get("label", item["id"])); button.custom_minimum_size = Vector2(44,44); button.toggle_mode = true; button.button_group = _group
+		button.pressed.connect(func() -> void: set_selected(String(item["id"]), true)); add_child(button); button.set_pressed_no_signal(String(item["id"]) == selected_id)
+	if not _presets.is_empty() and _selected_id.is_empty(): _selected_id = String(_presets[0].get("id", ""))
+func set_selected(id: String, emit_signal: bool = false) -> void:
+	for item: Dictionary in _presets:
+		if String(item.get("id", "")) == id:
+			_selected_id = id
+			if emit_signal: preset_selected.emit(id, int(item.get("value", 0)))
+			return
+func get_selected_id() -> String: return _selected_id
+func get_selected_value() -> int:
+	for item: Dictionary in _presets:
+		if String(item.get("id", "")) == _selected_id: return int(item.get("value", 0))
+	return 0