[ADD] website_sale_aplicoop: serve Eskaera per website

A co-op can run the plain shop on one website and the group orders on another,
but routes are registered process-wide: every /eskaera page answered on every
website of the database, and Odoo had already copied the Eskaera menu to all of
them.

`website.eskaera_enabled` decides which websites serve it, on by default so
installing changes nothing. It reaches the settings screen through `website_id`,
so it follows the website selector there. Where it is off the routes raise
NotFound and the menu is hidden.

The menu is hidden rather than deleted, by extending `_compute_visible`. That
keeps the record and any manual rename or reordering, so switching the feature
back on restores it as it was.

Note that a JSON route reports the 404 inside the JSON-RPC payload and still
answers HTTP 200; that is the transport, not a hole in the guard, and a test
pins it so the next reader does not take it for one.

The three remaining settings (lazy loading, products per page, low stock
threshold) are still `config_parameter`, so they stay global to the database.
Two websites share their values.

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

website_sale_aplicoop/tests/test_phase3_confirm_eskaera.py

@@ -69,6 +69,8 @@ def _build_request_mock(env, payload=None, website=None):
             show_line_subtotals_tax_selection="tax_excluded",
             fiscal_position_id=False,
             company_id=False,
+            # The Eskaera routes check that this website serves Eskaera.
+            eskaera_enabled=True,
         )
     request_mock = SimpleNamespace(
         env=env,