fix(seo): emit canonicals with the trailing slash the server actually serves

The hosting serves every route with a trailing slash and 307-redirects the bare form, while canonicals pointed at the bare form. trailingSlash: true aligns canonicals, internal links and Astro's trailingSlash setting with the served URLs, which the sitemap already used.

Author: begeistert

src/config.yaml

@@ -2,7 +2,9 @@ site:
   name: PyMCU
   site: 'https://pymcu.org'
   base: '/'
-  trailingSlash: false
+  # true = los canonicals y enlaces internos llevan barra final, igual que la URL
+  # que sirve el hosting (la variante sin barra responde 307 hacia la con barra).
+  trailingSlash: true
 
   # Vacio A PROPOSITO: el dominio esta verificado en Search Console por DNS, que
   # cubre todo el dominio y sobrevive a cualquier cambio de plantilla. NO reponer