feat(site): add sustainability footer, replace favicon, fix SEO URLs

- Replace default Astro favicon with minimal "CT" SVG (orange brand color)
- Delete unused favicon.ico
- Add carbon footprint disclosure to footer with Ecograder data (A+,
  0,001 g CO₂/visita, 10,7 kB, 100% green hosting)
- Add explicit "personal research project, not official" disclosure
- Update site URL to casesbuides.itziarzameza.dev across astro.config.mjs
  and Base.astro fallback

web/astro.config.mjs

@@ -29,7 +29,7 @@ function assetMimePlugin() {
 
 // https://astro.build/config
 export default defineConfig({
-  site: 'https://casestancades.vercel.app',
+  site: 'https://casesbuides.itziarzameza.dev',
   output: 'server',
   adapter: node({ mode: 'standalone' }),
   integrations: [sitemap()],

web/public/favicon.svg

@@ -1,9 +1,4 @@
-<svg xmlns="http://www.w3.org/2000/svg" fill="none" viewBox="0 0 128 128">
-    <path d="M50.4 78.5a75.1 75.1 0 0 0-28.5 6.9l24.2-65.7c.7-2 1.9-3.2 3.4-3.2h29c1.5 0 2.7 1.2 3.4 3.2l24.2 65.7s-11.6-7-28.5-7L67 45.5c-.4-1.7-1.6-2.8-2.9-2.8-1.3 0-2.5 1.1-2.9 2.7L50.4 78.5Zm-1.1 28.2Zm-4.2-20.2c-2 6.6-.6 15.8 4.2 20.2a17.5 17.5 0 0 1 .2-.7 5.5 5.5 0 0 1 5.7-4.5c2.8.1 4.3 1.5 4.7 4.7.2 1.1.2 2.3.2 3.5v.4c0 2.7.7 5.2 2.2 7.4a13 13 0 0 0 5.7 4.9v-.3l-.2-.3c-1.8-5.6-.5-9.5 4.4-12.8l1.5-1a73 73 0 0 0 3.2-2.2 16 16 0 0 0 6.8-11.4c.3-2 .1-4-.6-6l-.8.6-1.6 1a37 37 0 0 1-22.4 2.7c-5-.7-9.7-2-13.2-6.2Z" />
-    <style>
-        path { fill: #000; }
-        @media (prefers-color-scheme: dark) {
-            path { fill: #FFF; }
-        }
-    </style>
-</svg>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <rect width="64" height="64" rx="10" fill="#9a3412"/>
+  <text x="32" y="42" font-family="sans-serif" font-size="26" font-weight="700" text-anchor="middle" fill="#fafaf9">CT</text>
+</svg>

web/src/components/Footer.astro

@@ -23,6 +23,19 @@ const year = new Date().getFullYear();
         <a href="/metodologia" class="hover:text-orange-700">{t(lang, "nav.methodology")}</a>
       </nav>
     </div>
+    <p class="mb-2 text-sm text-stone-600 mt-6">
+      <strong class="text-stone-800">Projecte personal</strong> de recerca en
+      desenvolupament web sostenible i allotjament autoalojat. No és una
+      iniciativa oficial.
+    </p>
+    <p class="text-xs text-stone-500 leading-relaxed mt-2">
+      Petjada de carboni estimada:
+      <strong class="text-stone-700">0,001 g CO₂</strong> per visita ·
+      <strong class="text-stone-700">A+</strong> Digital Carbon Rating ·
+      allotjament 100% energia renovable ·
+      pes total <strong class="text-stone-700">10,7 kB</strong>.
+      Mesurat amb <a href="https://ecograder.com" class="underline hover:text-orange-700">Ecograder</a> (juliol 2026).
+    </p>
     <p class="text-xs text-stone-500 mt-6">
       © {year} Cases Tancades · CC BY-SA 4.0 ·
       <a href="https://github.com/itziarZG/Vivienda" class="hover:text-orange-700 underline underline-offset-2">codi font</a>

web/src/layouts/Base.astro

@@ -20,7 +20,7 @@ const fullTitle = title ? `${title} · ${t(lang, "site.title")}` : t(lang, "site
 const fullDescription = description ?? t(lang, "site.description");
 const siteTitle = t(lang, "site.title");
 
-const siteUrl = Astro.site?.toString().replace(/\/$/, "") ?? "https://casestancades.vercel.app";
+const siteUrl = Astro.site?.toString().replace(/\/$/, "") ?? "https://casesbuides.itziarzameza.dev";
 const canonicalUrl = `${siteUrl}${Astro.url.pathname}`;
 const ogImage = image ?? `${siteUrl}/og-image.png`;
 const ogLocale = lang === "es" ? "es_ES" : "ca_ES";