bug: version_cmp ignores prerelease labels, treats "1.5.0" and "1.5.0-alpha.3" as equal

### Packages versions

miden-vm: 0.30.0 (this bug is in scripts/lib/release-plan-common.sh, part of the repo's release tooling, not a published crate not really version-specific, but this is the current workspace version)

### Bug description

this time in scripts/lib/release-plan-common.sh. There is a function called version_cmp that checks whether a new version is actually newer than what is already published. The problem is it ignores prerelease labels like "-alpha.1". So it thinks "1.5.0" and "1.5.0-alpha.3" are the exact same version, when really 1.5.0 should count as newer.

This could cause a real release to get wrongly rejected as "not newer than what's already published" if the last published version was a prerelease.

I already have a fix ready with tests.

### How can this be reproduced?

1. source scripts/lib/release-plan-common.sh
2. Run: version_cmp "1.5.0" "1.5.0-alpha.3"
3. It prints 0 (equal). It should print 1, since 1.5.0 is the real release and should count as newer than its own alpha version.

### Relevant log output

```shell

```

The bug is in the `version_cmp` function in `scripts/lib/release-plan-common.sh`. Start by reading that file to understand the current version comparison logic. The fix must make the function recognize that a release version (e.g., '1.5.0') is newer than its prerelease (e.g., '1.5.0-alpha.3'). Test the fix by sourcing the script and running the example command from the issue to verify it returns 1.

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