refactor: make unused fields and functions private

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/modes/server/common.rs

@@ -28,8 +28,8 @@ pub struct ServerConfig {
 pub struct AppState {
     pub db: Arc<Mutex<rusqlite::Connection>>,
     pub data_dir: PathBuf,
-    pub password: Option<String>,
-    pub password_hash: Option<String>,
+    pub(crate) password: Option<String>,
+    pub(crate) password_hash: Option<String>,
 }
 
 #[derive(Serialize, Deserialize, ToSchema)]