chore: bump version to v3.1.1

- Update version in package.json, Cargo.toml, and tauri.conf.json
- Add CHANGELOG entries for v3.1.0 and v3.1.1

src-tauri/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "cc-switch"
-version = "3.0.0"
-description = "Claude Code MCP 服务器配置管理工具"
+version = "3.1.1"
+description = "Claude Code & Codex 供应商配置管理工具"
 authors = ["Jason Young"]
 license = "MIT"
 repository = "https://github.com/jasonyoung/cc-switch"