🔧 ci: fix Dockerfile.prod to use proper dependency hash and add testing scripts

scripts/calculate-deps-hash.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Calculate dependency hash for Docker cache tag
+# This script calculates the hash used for the build cache image tag
+
+# Calculate hash of go.mod + go.sum
+# Use shasum on macOS, sha256sum on Linux
+if command -v sha256sum >/dev/null 2>&1; then
+    DEPS_HASH=$(sha256sum go.mod go.sum | sha256sum | cut -d' ' -f1 | head -c 12)
+else
+    DEPS_HASH=$(shasum -a 256 go.mod go.sum | shasum -a 256 | cut -d' ' -f1 | head -c 12)
+fi
+
+echo "Dependency hash: $DEPS_HASH"
+echo "$DEPS_HASH"
+
+# Export for use in other scripts
+if [ -n "$1" ]; then
+    echo "DEPS_HASH=$DEPS_HASH" > "$1"
+    echo "Exported to: $1"
+fi