refactor(assets): move cosmic-stag to src/assets, rename grounds map

The PNG previously living at public/cosmic-stag.png was actually a
hand-drawn concept map of the property — rename it to property-map.png
so it's available when we wire it into Plan Your Visit or Concept.

The real cosmic-stag (with proper transparency) now lives at
src/assets/cosmic-stag.webp, imported from the three SFCs that use it
and referenced from index.html via a relative path. Vite hashes the
filename on build, so cache invalidation happens automatically and the
single import dedupes to one network fetch.

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

src/components/SiteFooter.vue

@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { useI18n } from 'vue-i18n'
+import cosmicStag from '@/assets/cosmic-stag.webp'
 
 const { t } = useI18n()
 const year = new Date().getFullYear()
@@ -10,7 +11,7 @@ const year = new Date().getFullYear()
     <div class="mx-auto grid max-w-7xl gap-8 px-4 py-10 lg:px-6 md:grid-cols-3">
       <div>
         <div class="mb-3 flex items-center gap-3">
-          <img src="/cosmic-stag.png" alt="" class="h-10 w-10" />
+          <img :src="cosmicStag" alt="" class="h-10 w-10" />
           <span class="font-serif text-lg">Château du Faune</span>
         </div>
         <p class="text-sm text-muted-foreground">{{ t('footer.tagline') }}</p>

src/components/SiteHeader.vue

@@ -2,6 +2,7 @@
 import { ref, computed, onMounted, onUnmounted, watch } from 'vue'
 import { useI18n } from 'vue-i18n'
 import { RouterLink, useRoute } from 'vue-router'
+import cosmicStag from '@/assets/cosmic-stag.webp'
 
 const { t, locale } = useI18n()
 const route = useRoute()
@@ -98,7 +99,7 @@ onUnmounted(() => {
     <div class="mx-auto max-w-7xl px-4 lg:px-6">
       <div class="flex h-16 items-center justify-between gap-4">
         <RouterLink to="/" class="flex items-center gap-3" @click="closeAll">
-          <img src="/cosmic-stag.png" alt="" class="h-9 w-9 shrink-0" />
+          <img :src="cosmicStag" alt="" class="h-9 w-9 shrink-0" />
           <span class="leading-tight">
             <span class="block font-serif text-base tracking-tight text-foreground">
               Château du Faune

src/views/HomeView.vue

@@ -1,6 +1,7 @@
 <script setup lang="ts">
 import { useI18n } from 'vue-i18n'
 import { RouterLink } from 'vue-router'
+import cosmicStag from '@/assets/cosmic-stag.webp'
 
 const { t } = useI18n()
 
@@ -88,7 +89,7 @@ const featuredEvents = [
         </div>
         <div class="relative flex items-center justify-center">
           <img
-            src="/cosmic-stag.png"
+            :src="cosmicStag"
             alt=""
             class="h-72 w-72 object-contain md:h-96 md:w-96"
           />