chore(docker): Update DockerFile to use NVIDIA distroless base image

[nv-mtucciarone]

Summary

• docker: base image alpine:latest → nvcr.io/nvidia/distroless/static:v4.0.0 (OSRB-approved base; required for CCluster container compliance)
• docker: drop USER 65532:65532 — the distroless base already runs as non-root (nvs, uid 1000)
• docker: drop curl — installed "for prestop script", but no preStop or lifecycle block exists in this chart, in examples/, or in the platform config that consumes this chart

static is the correct distroless variant: the binary is already built CGO_ENABLED=0 and needs no libc.

Test plan

• docker build passes
• Container runs and exits on its own config validation (Failed to load configuration), confirming the static binary executes on distroless

Notes

• Runtime uid changes 65532 → 1000. The chart sets no runAsUser/fsGroup and mounts only read-only secrets/configmaps (default mode 0644)
• Base image is publicly pullable — verified with an anonymous docker pull against an empty credential store, so no NGC key is needed in CI
• Publishing a new image requires a GitHub release; this PR changes the Dockerfile only. Chart version/appVersion (both 1.0.6) intentionally unchanged