refactor: update AppState references to use state module

- Change all instances of AppState to reference the new state module across multiple files for consistency.
- Clean up imports in auth, books, index_jobs, libraries, pages, search, settings, thumbnails, and tokens modules.
- Simplify main.rs by removing unused code and organizing middleware and route handlers under the new handlers module.

apps/api/src/settings.rs

@@ -7,7 +7,7 @@ use serde::{Deserialize, Serialize};
 use serde_json::Value;
 use sqlx::Row;
 
-use crate::{error::ApiError, AppState};
+use crate::{error::ApiError, state::AppState};
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct UpdateSettingRequest {