chore: ignore az bicep build output (infra/main.json)

- az bicep build --file infra/main.bicep emits a compiled ARM template
  that was previously untracked; ignore it as generated build output

Author: Aitomates

.gitignore

@@ -4,4 +4,5 @@
 *.local.bicepparam
 *.whatif.json
 *.whatif.txt
+infra/main.json