Update version to 0.1.2 and enhance command line arguments

- Bump `gatekeeper` version to 0.1.2 in `Cargo.toml` and `Cargo.lock`.
- Add new command line arguments for upstream idle timeout and HTTP/2 support in the `Gateway` struct.
- Refactor proxy logic to conditionally set HTTP version and idle timeout based on new arguments.

Author: h2cone

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 All notable changes to this project will be documented in this file.
 
+## [v0.1.2] - 2025-07-12
+
+* Add command line arguments for upstream idle timeout and HTTP/2 support
+* Refactor proxy logic to conditionally set HTTP version and idle timeout based on new arguments
+
 ## [v0.1.1] - 2025-03-26
 
 * Update `env_logger` and `openssl` dependencies