Add version checking and force upgrade functionality to upgrade.sh

[LaurenceJJones]

fix #77

Features added:
- Version comparison between current and new binaries
- Smart upgrade detection (skips if versions are same or new version is older)
- Force upgrade option (--force/-f) to override version checks
- Help option (--help/-h) with usage information
- User confirmation prompt for interactive upgrades
- Informative messages about version differences

This addresses user requests for:
- Checking if upgrade is actually needed before proceeding
- Ability to force upgrade when building from source
- Better user experience with clear feedback about version changes

Functions added to _bouncer.sh:
- get_bouncer_version(): Extract version from binary --version output
- version_compare(): Compare semantic versions (major.minor.patch)
- check_upgrade_needed(): Main logic for upgrade decision making

[sabban]

I would rather keep this file as much as the same as the other bouncer.

I am not against it, but if changed here maybe it's worth changing it for every bouncer.

[mmetc]

A few things

• the _bouncer.sh script is supposed to be common functions for all the "similar" bouncers, are you proposing this for the firewall, custom etc. RCs as well?
• package managers like apt allow prompts and any interactive flow through the distribution plumbing, see debconf templates for example: https://goreleaser.com/cookbooks/debconf-templates/
• weird pattern matching
• If the use case is "install from sources", the user is perfectly capable to decide if they want to upgrade or not, I think by comparing the version numbers we are scratching an itch we don't have