feat(integrations): add the integrations directory pages

[datlechin]

• /integrations in 12 languages and /integrations/{slug} in English, from resources/data/integrations.json. Static route patterns; IntegrationPages decides which detail pages exist. /vi/integrations/{slug} is a 404 that offers the English page.
• Hub: search plus category, TablePro app and type filters, as ruled rows. One function (components/integrations/model.ts) filters in SSR and the browser; the GET form works without JavaScript and the address bar is replaced, not pushed.
• Another language lists an entry only while its tagline there was translated from the current summary. Taglines for the six built-in entries in 12 languages.
• Detail page: install action by type, What it uses, Report a problem (registry form, slug filled in), disclaimer and rel="ugc nofollow" for Community entries.
• JSON-LD: CollectionPage/ItemList and WebPage/BreadcrumbList. Generic OG card. Detail pages go in the sitemap in English; archived ones are noindex and left out.
• Links from the footer Product group and /features/ai-mcp#automation.
• integrations joins the content guards' data files. Design system §8.21-8.22 record the hub as the one filter page; docs/architecture.md covers the pages.
• The hub copy, labels and taglines in 11 languages need your review. de, fr and it keep Partner, Community, Schemas and Type as in English (added to ContentParityTest's same-words list).
• The hub is empty until the first sync PR lands.

Screenshots with the six built-in entries from TableProApp/integrations#2 (data not committed):