Fix localisation support and expand website docs

Bug fix

Non-English localisations now work. macOS uses the main bundle's CFBundleLocalizations array to decide which languages the process can resolve. Without entries for shipped languages, String(localized:bundle:) fell back to English even when the inner SPM resource bundle had the correct .lproj. All five shipped localisations (English, Armenian, Italian, Polish, Simplified Chinese) are now listed in Info.plist. Thanks to @bovirus for the report.

New Pro page at whatcable.uk/pro with feature showcase, pricing, and checkout.
New post-purchase success page with activation instructions.
New support form (licence-gated) with FAQ.
Expanded docs page with jump-to navigation, inline screenshots, full Pro feature reference, and troubleshooting FAQ.
Standardised nav and footer across all pages.