fix(CAR-812): correct receipt email format and --env flag parser

- docs: fix email address format to receipts+<token>@receipts.cartsnitch.com
  (per Settings → Receipt Email UI, not the old farh.net domain format)
- docs: fix UI section label from 'Account' to 'Receipt Email'
- scripts/seed-env.sh: fix --env flag parser when called as './seed-env.sh --env uat'
  positional form was already correct; flag form was consuming --env as ENV value

Co-Authored-By: Paperclip <noreply@paperclip.ing>

scripts/seed-env.sh

@@ -22,8 +22,10 @@
 set -euo pipefail
 
 # --- Config -------------------------------------------------------------------
-ENV="${1:-dev}"
-shift || true
+ENV="dev"
+if [[ "${1:-}" == "dev" || "${1:-}" == "uat" ]]; then
+  ENV="$1"; shift
+fi
 
 while [[ $# -gt 0 ]]; do
   case "$1" in