Remove Dead Code

[lowhung]

Description

Remove unused fields marked with #[allow(dead_code)] that are no longer needed.

Current State

// src/ui/app.rs:28
#[allow(dead_code)]
egui_graph: Graph<ModuleNode, TopicEdge>,

// src/ui/app.rs:59
#[allow(dead_code)]
sound_enabled: bool,

Proposed Solution

1. Remove egui_graph field entirely (unused, was likely for egui_graphs integration that was not completed)
2. Either implement sound feature or remove sound_enabled field

Acceptance Criteria

• Remove egui_graph field and its initialization
• Remove sound_enabled field (or create ticket to implement sound)
• Remove corresponding imports if no longer needed
• All tests pass

Files Affected

• src/ui/app.rs