fix(deploy): unify backend URL policy

scripts/test-backend-url-policy.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+set -eu
+
+cd "$(dirname "$0")/.."
+
+policy=frontend/src/api/backend-url-policy.json
+corpus=frontend/src/api/backend-url-cases.json
+
+jq -c '.[]' "$corpus" | while IFS= read -r case_json; do
+  value=$(printf '%s' "$case_json" | jq -r '.value')
+  valid=$(printf '%s' "$case_json" | jq -r '.valid')
+  if BACKEND_URL_POLICY_FILE="$policy" ./docker/validate-backend-url.sh "$value"; then
+    actual=true
+  else
+    actual=false
+  fi
+  if [ "$actual" != "$valid" ]; then
+    echo "shell policy mismatch for BACKEND_BASE_URL=$value: expected $valid" >&2
+    exit 1
+  fi
+done
+
+echo "shell canonical URL corpus: ok"