feat: Add multiarch support to csi-snapshot-metadata Dockerfile

Make grpc-health-probe download multiarch-compatible by:
- Adding TARGETARCH build argument
- Using grpc_health_probe-linux-${TARGETARCH} instead of hardcoded amd64
- Adding --platform=$BUILDPLATFORM to builder stage for cross-compilation

This enables building for both linux/amd64 and linux/arm64 platforms.

Tested with podman build --platform linux/amd64,linux/arm64

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: kaovilai

cmd/csi-snapshot-metadata/Dockerfile

@@ -1,6 +1,7 @@
-FROM alpine AS builder
+FROM --platform=$BUILDPLATFORM alpine AS builder
 ARG GRPC_HEALTH_PROBE_VERSION=v0.4.37
-ADD https://github.com/grpc-ecosystem/grpc-health-probe/releases/download/${GRPC_HEALTH_PROBE_VERSION}/grpc_health_probe-linux-amd64 /bin/grpc_health_probe
+ARG TARGETARCH
+ADD https://github.com/grpc-ecosystem/grpc-health-probe/releases/download/${GRPC_HEALTH_PROBE_VERSION}/grpc_health_probe-linux-${TARGETARCH} /bin/grpc_health_probe
 RUN chmod +x /bin/grpc_health_probe
 
 FROM gcr.io/distroless/static:latest