feat(deeplink): add config file support for deeplink import

Support importing provider configuration from embedded or remote config files.
- Add base64 dependency for config content encoding
- Support config, configFormat, and configUrl parameters
- Make homepage/endpoint/apiKey optional when config is provided
- Add config parsing and merging logic

src-tauri/Cargo.toml

@@ -50,6 +50,7 @@ tempfile = "3"
 url = "2.5"
 auto-launch = "0.5"
 once_cell = "1.21.3"
+base64 = "0.22"
 
 [target.'cfg(any(target_os = "macos", target_os = "windows", target_os = "linux"))'.dependencies]
 tauri-plugin-single-instance = "2"