feat: add support for salted password hash authentication

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/args.rs

@@ -143,6 +143,10 @@ pub struct OptionsArgs {
     #[arg(help("Password for server authentication (requires --server)"))]
     pub server_password: Option<String>,
 
+    #[arg(long, env("KEEP_SERVER_PASSWORD_HASH"))]
+    #[arg(help("Password hash for server authentication (requires --server)"))]
+    pub server_password_hash: Option<String>,
+
     #[arg(long, help("Force output even when binary data would be sent to a TTY"))]
     pub force: bool,
 }