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/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "CC Switch",
-  "version": "3.0.0-beta.1",
+  "version": "3.0.0",
   "identifier": "com.ccswitch.app",
   "build": {
     "frontendDist": "../dist",