feat(i18n): add fr_CA translation and apply string context rule #minor

[Revenantal]

Context

Wicket: none
Related PRs: industrialdev/wicket-wp-base-plugin#63, industrialdev/wicket-wp-account-centre#58, industrialdev/wicket-wp-financial-fields#10

What

• Adds languages/wicket-theme.pot and a Canadian French (fr_CA) translation (.po, .mo, .l10n.php) for all 788 strings, including ACF field strings and plurals.
• Applies the short-string context rule across the theme and its ACF field strings.
• Scopes ACF translation to the theme's own fields and merges split strings.

Why

Theme strings were missing context, some were glued together from fragments, and ACF translation used a site-wide filter that affected plugin and child-theme field groups. Wicket now ships fr_CA, following the Atlas translations convention (conv.stack.translations).

How

Contexts and strings

• Every 1 to 3 word string gets a gettext context that names its kind. Full sentences drop their contexts.
• "Published:", "Results for:", "Displaying:" and "Search Results for:" are merged with their values into whole strings. The publish date now uses the site date format, and the breadcrumb search term is escaped.
• Search and listing result counts use real plurals.
• Translator comments are added to ambiguous strings that already existed on main. Their msgids are unchanged, so the legacy wicket domain fallback still works.
• The product button now reads "Log in to Purchase" (verb).

ACF

• An acf/prepare_field filter replaces the site-wide acf/settings/l10n_textdomain filter. It translates only fields from the theme's acf-json.
• composer i18n:acf generates languages/acf-strings.php for make-pot.

Fixes and tooling

• Replaces the nonexistent esc_html_ex() with echo esc_html_x(). It would have fataled on the fallback index template and the pagination demo.
• The .pot hook runs faster, supports .ci/pot-exclude, and excludes font-awesome/.

Impact on existing translations

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 theme. Site-level translations (Loco, wp-content/languages) still take precedence.

[EstebanForge]

Approved. Third PR, same bar, and it holds. What I verified:

• msgfmt --check passes on the fr_CA catalog (771 messages), the shipped .mo matches, .l10n.php and acf-strings.php (516 ACF strings) are valid, and the CI pot check is green.
• style.css only gains the Text Domain and Domain Path headers. No manual version bump, the release bot stays in charge.
• load_theme_textdomain runs inside wicket_setup() on after_setup_theme, and the fr_CA.mo naming matches the theme convention. The legacy wicket fallback filters follow the same four-variant pattern as the base plugin, registered before init. Cross-package behavior is consistent.
• The ACF translator is key-guarded to this theme's own acf-json, and the generator is the same one as account-centre with the theme paths swapped.
• post-types.php fixes the old untranslatable patterns: _x($singular) variable msgids and 'Add New ' . $singular fragments are now proper %s templates. Raw slugs stay untranslated on purpose, with a comment saying why. Good.
• The dead hide-wp-admin-notifications textdomain loader is gone (its path never existed), and those strings moved to wicket-theme.

Two notes, nothing to fix:

1. The listing sort labels came from a third dead domain, industrial, not wicket. The fallback only covers wicket, so any client that translated those four strings through an industrial textdomain loses them. Same accepted risk class as the other PRs, just a different corpse.
2. One ACF instruction string ("Use this to add custom fonts from CDN...") contains a literal \r\n in the source, and the fr translation mirrors it, so msgfmt emits a warning. Harmless, but cleaning the source string someday would silence it.

Thanks Adrian, the set is consistent across the three packages.