fix: Remove unused variable warning and add release build script

- Fix unused `project_path` parameter warning in make_executable()
- Add build-release.sh for automated binary packaging
- Update .gitignore to exclude release artifacts
- Support cross-compilation for Linux and Windows binaries

Release artifacts are now built with ./build-release.sh and uploaded
to Gitea releases separately, keeping the git repo clean.

src/project/mod.rs

@@ -434,14 +434,14 @@ class BasicTest {
         Ok(())
     }
     
-    fn make_executable(&self, project_path: &Path) -> Result<()> {
+    fn make_executable(&self, _project_path: &Path) -> Result<()> {
         #[cfg(unix)]
         {
             use std::os::unix::fs::PermissionsExt;
             
             let scripts = vec!["gradlew", "build.sh", "deploy.sh"];
             for script in scripts {
-                let path = project_path.join(script);
+                let path = _project_path.join(script);
                 if path.exists() {
                     let mut perms = fs::metadata(&path)?.permissions();
                     perms.set_mode(0o755);