Add a blog, built from pages

A post is a page in the panel's "Blog" category, so it is written,
translated, scheduled and reviewed like any page, and the MCP server
can publish one the same way. Nothing new in the API.

- /blog (/en/blog, /ca/blog): posts newest first, with image, date and
  excerpt.
- A post shows its date and leads back to the blog; its structured data
  is a BlogPosting.
- /blog/rss.xml?lang=xx: one feed per language, announced in <head>.
- Posts stay out of the header and the footer, which links the blog
  once there is any post instead of growing with every one.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

landing/src/app/core/copy.ts

@@ -128,6 +128,15 @@ export interface Copy {
     otherWays: string;
     otherWaysLead: string;
   };
+  blog: {
+    eyebrow: string;
+    title: string;
+    lead: string;
+    empty: string;
+    readMore: string;
+    published: string;
+    feed: string;
+  };
   service: {
     eyebrow: string;
     projects: string;
@@ -301,6 +310,15 @@ const es: Copy = {
     otherWays: 'Otras formas de ayudar',
     otherWaysLead: 'También necesitamos diseño, documentación, traducciones y gente que pruebe lo que hacemos. Escríbenos y lo hablamos.',
   },
+  blog: {
+    eyebrow: 'Blog',
+    title: 'Novedades',
+    lead: 'Lo que estamos haciendo, lo que hemos aprendido y lo que viene.',
+    empty: 'Todavía no hemos publicado nada. Vuelve pronto.',
+    readMore: 'Leer',
+    published: 'Publicado el',
+    feed: 'Suscríbete por RSS',
+  },
   service: {
     eyebrow: 'Servicio',
     projects: 'Trabajo relacionado',
@@ -487,6 +505,15 @@ const en: Copy = {
     otherWays: 'Other ways to help',
     otherWaysLead: 'We also need design, documentation, translations and people to try what we build. Write to us and we will talk it over.',
   },
+  blog: {
+    eyebrow: 'Blog',
+    title: 'News',
+    lead: 'What we are working on, what we have learned and what comes next.',
+    empty: 'We have not published anything yet. Come back soon.',
+    readMore: 'Read',
+    published: 'Published on',
+    feed: 'Subscribe via RSS',
+  },
   service: {
     eyebrow: 'Service',
     projects: 'Related work',
@@ -673,6 +700,15 @@ const ca: Copy = {
     otherWays: "Altres maneres d'ajudar",
     otherWaysLead: 'També necessitem disseny, documentació, traduccions i gent que provi el que fem. Escriu-nos i en parlem.',
   },
+  blog: {
+    eyebrow: 'Blog',
+    title: 'Novetats',
+    lead: 'El que estem fent, el que hem après i el que ve.',
+    empty: 'Encara no hem publicat res. Torna aviat.',
+    readMore: 'Llegir',
+    published: 'Publicat el',
+    feed: "Subscriu-t'hi per RSS",
+  },
   service: {
     eyebrow: 'Servei',
     projects: 'Feina relacionada',