ci(containers): add semver image tags on release and remove path filt…

…ers (#294)

* ci(containers): add semver image tags on release and remove path filters

- Trigger on version tags (v*.*.*) in addition to main branch pushes
- Add semver tags (version, major.minor, major) for tag-triggered builds
- Add `latest` tag only for stable (non-prerelease) release tags
- Remove `latest` from main branch pushes (latest = last tagged release)
- Remove path filters so every main merge rebuilds images

* fix(ci): gate floating semver tags to stable releases only

Pre-release tags (e.g. v1.0.0-rc.1) should only produce the full version
tag, not move the major.minor or major floating tags. Gate those patterns
with the same !contains(github.ref_name, '-') condition used for latest.