improve simplified-mode platform checks and standardize image build D…

[jimmieme]

Fixed admin init directory creation check in:
- MemberManageService

• Updated platform status interceptor:
  • In simplified mode (enableInternetAccess = false), skip external product
    platform probing.
  • Return existing product-platform error contract without repeated noisy
    connectivity checks.
• Docker build updates:
  • Added Dockerfile.jvm.build for build-and-package flow (compile during
    image build).
  • Added Dockerfile.jvm.prebuilt for packaging prebuilt target/quarkus- app.
  • Updated Dockerfile.jvm to use a modern multi-stage JDK 17 build path.

Why

• Simplified deployments intentionally disable internet/platform access, so
  product platform probing creates avoidable error noise.
• We need reproducible and explicit Docker build paths for both CI-style builds
  and prebuilt artifact workflows.

Validation

• Gateway image builds successfully with Dockerfile.jvm.build.
• Existing API behavior remains compatible; only simplified-mode probing
  behavior is tightened.
• Compose references are consistent with the new Dockerfile structure.

Impact

• Scope is space-gateway only.
• No breaking API contract changes.
• Improves operational clarity and deployment consistency.

Generated-by: Codex