feat(QOV-1954): add --ephemeral flag with clone/debug modes to qovery shell

[Guimove]

Jira: https://qovery.atlassian.net/browse/QOV-1954

Summary

• Adds --ephemeral flag to qovery shell
• Adds --mode flag (clone or debug) to control the ephemeral behavior
• When --ephemeral is set, routes to /shell/ephemeral instead of /shell/exec
• --mode clone (default): spawns a new isolated pod from the service image (Heroku-style, HIPAA-safe)
• --mode debug: injects an ephemeral container into an existing running pod (kubectl-debug style, shares network/PID namespace)
• Warning printed if --mode is set without --ephemeral

Usage

# Normal shell (existing behavior)
qovery shell

# Ephemeral shell -- clone mode (new isolated pod, default)
qovery shell --ephemeral --mode clone \
  --organization myorg --project myproject --environment myenv --service myservice

# Ephemeral shell -- debug mode (inject into existing pod)
qovery shell --ephemeral --mode debug \
  --organization myorg --project myproject --environment myenv --service myservice

# Custom command (e.g. Django shell_plus)
qovery shell --ephemeral --mode clone --command python,manage.py,shell_plus \
  --organization myorg --project myproject --environment myenv --service myservice

# Via console URL
qovery shell --ephemeral --mode clone <qovery_console_service_url>

Depends on

rust-backend MR !635 must be merged and deployed first: https://gitlab.com/qovery/backend/rust-backend/-/merge_requests/635

The new /shell/ephemeral WebSocket endpoint is implemented there.

Test plan

• qovery shell (no flag) -- verify existing behavior unchanged
• qovery shell --ephemeral --mode clone -- interactive selection, verify new pod spawns and is deleted on exit
• qovery shell --ephemeral --mode clone -- pod deleted on Ctrl+C
• qovery shell --ephemeral --mode debug -- verify ephemeral container injected into existing pod
• qovery shell --ephemeral --mode clone --command python,manage.py,shell_plus -- custom command
• qovery shell --mode clone (without --ephemeral) -- verify warning printed, normal shell opened
• Via console URL with --ephemeral --mode clone