feat: make gosu optional in docker entrypoint for hardened containers

[R-Panic]

Description

Fixes issue where containers running with hardened security context (non-root user) fail because gosu cannot switch users from a non-root context.

Problem

When Kubernetes/OCP securityContext specifies:

securityContext:
  runAsUser: 10001
  runAsGroup: 10001
  fsGroup: 10001
  runAsNonRoot: false

The entrypoint fails with:

error: failed switching to "subtensor": operation not permitted

Solution

1. Auto-detect if already running as subtensor user and skip gosu
2. Add SKIP_GOSU=true environment variable for explicit control
3. Maintain backward compatibility with root-to-non-root transitions

Changes

scripts/docker_entrypoint.sh:

• Check current user before calling gosu
• Skip gosu if running as subtensor user or SKIP_GOSU=true

Testing

• Backward compatible: root containers still use gosu
• Non-root containers with subtensor user skip gosu
• Works with Kubernetes hardened security contexts
• SKIP_GOSU=true provides explicit override

Fixes #2475

Signed-off-by: R-Panic bot@term.com