feat: add centralized API service layer for frontend

- Create frontend/src/api/mod.rs with centralized HTTP client and error handling
- Implement api::auth module (login, logout, check_auth, get_user)
- Implement api::torrent module (add, action, delete, start, stop, set_label, set_priority)
- Implement api::setup module (get_status, setup)
- Implement api::settings module (set_global_limits)
- Implement api::push module (get_public_key, subscribe)
- Update all components to use api service layer instead of direct gloo_net calls
- Add thiserror dependency for error handling

frontend/src/lib.rs

@@ -1,8 +1,8 @@
 mod app;
-// mod models; // Removed
 mod components;
 pub mod utils;
 pub mod store;
+pub mod api;
 
 use leptos::*;
 use wasm_bindgen::prelude::*;