refactor: rename core module to services

Co-authored-by: aider (openai/andrew/openrouter/google/gemini-2.5-pro) <aider@aider.chat>

src/modes/get.rs

@@ -3,7 +3,7 @@ use std::io::{Write};
 
 use crate::common::is_binary::is_binary;
 use crate::config;
-use crate::core::item_service::ItemService;
+use crate::services::item_service::ItemService;
 use clap::Command;
 use is_terminal::IsTerminal;
 use std::path::PathBuf;