feat: parameterize seed tooling for UAT + document UAT receipt-submission path

- Add scripts/seed-env.sh with --env dev|uat argument, replacing hardcoded namespace
- Keep scripts/seed-dev.sh as one-line wrapper calling seed-env.sh dev
- Add scripts/seed-env-job.yaml with __ENV__ placeholder for namespace/label
- Add scripts/apply-seed-job.sh <env> helper using sed substitution
- Keep scripts/seed-dev-job.yaml as unchanged backward-compat copy
- Add docs/uat-receipt-submission.md documenting the inbound email receipt path for UAT

Refs: CAR-812, CAR-808

scripts/apply-seed-job.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# =============================================================================
+# apply-seed-job.sh — Apply the seed Job manifest for a given environment.
+#
+# Usage:
+#   ./apply-seed-job.sh <env>
+#
+# Example:
+#   ./apply-seed-job.sh uat
+#   ./apply-seed-job.sh dev
+# =============================================================================
+
+set -euo pipefail
+
+ENV="${1:-}"
+HELP_FLAG=""
+
+while [[ $# -gt 0 ]]; do
+  case "$1" in
+    --help) HELP_FLAG="1"; shift ;;
+    *) ENV="$1"; shift ;;
+  esac
+done
+
+if [[ -n "$HELP_FLAG" ]] || [[ -z "$ENV" ]]; then
+  echo "Usage: $0 <env>"
+  echo "  env   dev or uat"
+  exit 0
+fi
+
+if [[ "$ENV" != "dev" && "$ENV" != "uat" ]]; then
+  echo "ERROR: Invalid environment: $ENV (must be 'dev' or 'uat')" >&2
+  exit 1
+fi
+
+SCRIPT_DIR="$(dirname "$0")"
+sed "s/__ENV__/${ENV}/g" "${SCRIPT_DIR}/seed-env-job.yaml" | kubectl apply -f -
+echo "Seed job applied for environment: $ENV"