Add ca.po for both addons, matching the existing es/eu coverage
(378 and 4 entries respectively). Add the missing "ca" fallback block
in website_sale_i18n.py alongside the existing es/eu ones, and correct
the i18n README, which falsely claimed complete pt/gl/fr/it coverage
that was never actually present.
Add hardcoded fallback translations for es/eu when PO-based translation
returns the source string unchanged. Expand labels dict with all keys
needed by the frontend. Fix JSON response parsing in template
(data.result || data). Add js_translations keys. Add pot file for
stock_picking_batch_custom.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>