feat(home/hero): swap stag still for autoplaying morph video

Replace the static cosmic-stag.avif in the hero with an autoplaying,
muted, looping <video> of the morph (webm), falling back to a still
WebP frame inside the <video> for browsers that can't play any
<source>. Standards-compliant fallback pattern; assets imported via
Vite so they get content-hashed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/views/HomeView.vue

@@ -3,7 +3,8 @@ import { useI18n } from 'vue-i18n'
 import { RouterLink } from 'vue-router'
 import { Button } from '@/components/ui/button'
 import { Card, CardContent } from '@/components/ui/card'
-import cosmicStag from '@/assets/cosmic-stag.avif'
+import cosmicStagMorphWebm from '@/assets/cosmic-stag-morph-1024.webm'
+import cosmicStagMorphFallback from '@/assets/cosmic-stag-morph-fallback.webp'
 import heroLandscape from '@/assets/hero-landscape.webp'
 import sectionTile from '@/assets/section-tile.webp'
 
@@ -74,11 +75,17 @@ const featuredEvents = [
         >
           Château du Faune
         </h1>
-        <img
-          :src="cosmicStag"
-          alt=""
+        <video
+          autoplay
+          muted
+          loop
+          playsinline
+          aria-hidden="true"
           class="mt-4 h-80 w-80 object-contain md:h-[28rem] md:w-[28rem] lg:h-[36rem] lg:w-[36rem] xl:h-[42rem] xl:w-[42rem]"
-        />
+        >
+          <source :src="cosmicStagMorphWebm" type="video/webm" />
+          <img :src="cosmicStagMorphFallback" alt="" />
+        </video>
       </div>
     </section>