chore: prepare v3.0.0 release

- Bump version to 3.0.0 across all files
- Update Cargo.toml with proper package metadata
- Rename crate from 'app' to 'cc-switch'
- Use Rust edition 2024 with minimum rust-version 1.85.0
- Update library name to cc_switch_lib

src-tauri/src/main.rs

@@ -2,5 +2,5 @@
 #![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
 
 fn main() {
-  app_lib::run();
+  cc_switch_lib::run();
 }