[I18N] website_sale_lazy_loading: add es, ca, eu and gl translations

All 13 terms of the POT, in the four languages, generated with polib from
the POT Odoo exported.

The wording follows what website_sale_aplicoop already says on the same
site, so the two shops do not name the same thing twice: "Cargar más
productos" / "Carrega més productes" / "Produktu gehiago kargatu",
"Produktuak Orrialdeko", and "karga geldoa" for lazy loading. The selection
labels are repeated verbatim inside the field help, so what the settings
page offers and what the help describes read as the same three options.

The two view terms carry markup: the globe icon of the website-specific
hint and the spinner next to the loading message. Both keep their tags and
attributes untouched, and only the human text -- the icon's title, the
message -- is translated. Note that Odoo leaves that globe title in English
in its own es and ca files; here it is translated, as it is the one thing
in that span a visitor can read.

Also moves the POT under i18n/, where Odoo looks for it and where the rest
of the addons keep theirs.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

website_sale_lazy_loading/README.rst

@@ -100,6 +100,7 @@ Technical
     models/website.py             shop_lazy_loading (per website)
     views/..._templates.xml       shared grid template + lazy loading block
     static/src/js/...             public widget appending the pages
+    i18n/                         es, ca, eu, gl (complete)
 
 Tests: ``docker-compose run --rm odoo odoo $ODOO_ADDONS -d odoo --test-enable
 --stop-after-init -u website_sale_lazy_loading``