fix: quick wins (#7, #9, #13)

- Add --version flag and log version on startup (closes #9)
- URL-escape ref query parameter in GetFileContentRef (closes #7)
- Add go vet to release workflow (closes #13)

Renamed local url variable to reqURL to avoid shadowing net/url package.

cmd/review-bot/main.go

@@ -18,6 +18,7 @@ import (
 var version = "dev"
 
 func main() {
+	versionFlag := flag.Bool("version", false, "Print version and exit")
 	// CLI flags
 	giteaURL := flag.String("gitea-url", envOrDefault("GITEA_URL", ""), "Gitea instance URL")
 	repo := flag.String("repo", envOrDefault("GITEA_REPO", ""), "Repository (owner/name)")
@@ -36,6 +37,13 @@ func main() {
 
 	flag.Parse()
 
+	if *versionFlag {
+		fmt.Printf("review-bot %s\n", version)
+		os.Exit(0)
+	}
+
+	log.Printf("review-bot %s", version)
+
 	// Validate required fields
 	if *giteaURL == "" || *repo == "" || *prNum == "" || *reviewerToken == "" ||
 		*llmBaseURL == "" || *llmAPIKey == "" || *llmModel == "" {