feat(media): support external https image urls for entities

Allow entities to use full https:// URLs as their image path
Validate external URLs to prevent http://, data:, or credentials
Update API responses and frontend components to handle external sources

frontend/src/views/PokemonEdit.vue

@@ -586,12 +586,17 @@ function pokemonImageLabel(image: PokemonImage) {
   if (image.source === 'upload') {
     return t('media.uploadedImage');
   }
+  if (image.source === 'external') {
+    return t('media.image');
+  }
   return `${image.version} - ${image.variant}`;
 }
 
 function pokemonImageAlt(image: PokemonImage) {
   const name = pokemonForm.value.name.trim() || (pokemonForm.value.id.trim() ? `#${pokemonForm.value.id.trim()}` : t('pages.pokemon.title'));
-  return image.source === 'upload' ? t('media.imageAlt', { name }) : t('pages.pokemon.imageAlt', { name, variant: image.variant });
+  return image.source === 'upload' || image.source === 'external'
+    ? t('media.imageAlt', { name })
+    : t('pages.pokemon.imageAlt', { name, variant: image.variant });
 }
 
 function selectPokemonImage(image: PokemonImage) {