Add graph explorer components, API handlers, and dependency updates

Adds code inspector, file tree components, graph visualization JS,
graph API handlers, sidebar navigation updates, and misc improvements.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compliance-agent/src/api/routes.rs

@@ -43,6 +43,10 @@ pub fn build_router() -> Router {
             "/api/v1/graph/{repo_id}/search",
             get(handlers::graph::search_symbols),
         )
+        .route(
+            "/api/v1/graph/{repo_id}/file-content",
+            get(handlers::graph::get_file_content),
+        )
         .route(
             "/api/v1/graph/{repo_id}/build",
             post(handlers::graph::trigger_build),