fix(cli): exit with non-zero status when configure receives an invalid API URL (#3356)

Previously, `hindsight configure --api-url <invalid>` printed an error
but returned exit code 0 because the validation block called
`print_error!` followed by `return Ok(())`. Scripts and CI pipelines
relying on the exit code could not detect the failure.

Replace the silent success with `anyhow::bail!` so the top-level error
handler prints the message and exits with status 1, matching the
behavior of every other CLI error path.

Add two integration tests:
- configure rejects URLs missing http(s):// with non-zero exit
- configure accepts both http:// and https:// URLs