pkg/compose: use negotiated API version for request shaping

Move runtimeVersionCache from a package-level var to per-instance fields
on composeService and add CurrentAPIVersion() that negotiates via Ping
before returning the client version.

Switch getCreateConfigs and buildContainerVolumes to use
CurrentAPIVersion so that version-gated request shaping matches what
the daemon actually validates against (the negotiated API version from
the request path, not the server's max capability).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Guillaume Lours <glours@users.noreply.github.com>