feat(i18n): move to wicket-base text domain and add fr_CA translation #minor

[Revenantal]

Context

Wicket: none
Related PRs: industrialdev/wicket-wp-account-centre#58, industrialdev/wicket-wp-theme#19, industrialdev/wicket-wp-financial-fields#10

What

• Moves the base plugin from the shared wicket text domain to wicket-base. If a string has no wicket-base translation, it falls back to wicket.
• Adds languages/wicket-base.pot and a Canadian French (fr_CA) translation (.po, .mo, .l10n.php) for all 369 strings.
• Adds a pre-commit hook that regenerates the .pot, and a PR check that fails when the .pot is out of date.

Why

Base strings were spread across foreign domains (wicket-child, sassquatch, woocommerce-memberships*, and others), had no context, and were often built from fragments. That made them hard or impossible to translate. Wicket now ships fr_CA, following the Atlas translations convention (conv.stack.translations).

How

Text domain

• WicketWP\Language loads languages/ and falls back to the wicket domain, so existing Loco/WPML translations still apply.
• Strings on foreign domains move to wicket-base. Real WooCommerce and Event Tickets Plus strings keep their own domains.

String cleanup

• Short strings (1 to 3 words) get a context that names the kind of string, as the short-string context rule says.
• Fragments become whole strings ("Go back to %s", "Related %s", "Tab %d", and others). Account widget errors are built with WicketWP\Widgets\FormErrors and the output is escaped.
• Placeholder strings get translator comments, and plurals use real plural forms.
• Fixes English typos and a broken <em> tag.

Tooling

• composer setup-hooks installs the pre-commit .pot hook. The hook never blocks a commit.

Impact on existing translations

Changed or re-contexted strings no longer match existing site translations. We accepted this because client translation coverage is under 1% and fr_CA now ships with the plugin. Site-level translations (Loco, wp-content/languages) still take precedence.

[EstebanForge]

Approved. The migration itself checks out.

Two items I'd fix in a follow-up (neither blocks the merge):

1. includes/components/org-search-select.php:974 still calls _e('Search for your', 'wicket'). It's the only string left on the old domain. It never lands in wicket-base.pot, so the CI drift check and Loco can't see it. Please move it to _x('Search for your', 'label', 'wicket-base').

2. The FormErrors::field_message() docblock says API error titles get looked up in the plugin domain. The actual call is a context-free translate($message, 'wicket-base'), and catalog entries like "can't be blank" live under msgctxt "message", so that lookup can never match and those titles stay English. Same behavior as the old code, so no regression, but other packages will copy this class. Please fix the lookup or the comment.

Thanks Adrian, nice work on the fallback design :)