chore: gitignore compiled ARM template and preflight artifacts

Author: marktayl1

.gitignore

@@ -471,4 +471,9 @@ __pycache__/
 data/sample_code/
 # Bicep local files
 *.local*.bicepparam
-*.local*.parameters.json
+*.local*.parameters.json
+
+# Compiled ARM template (regenerated by azd provision)
+infra/main.json
+# Preflight check artifacts
+infra/preflight-*.bicepparam