make upload and metadata UI responsive on mobile.

Improve narrow-viewport layout for upload, About, and shell overflow; keep modal scroll without extra dismiss or a11y markup changes.

frontend/src/components/upload/UploadIntakeControls.vue

@@ -1,12 +1,12 @@
 <template>
     <div class="flex w-full flex-col gap-3">
-        <p class="mb-3 text-base text-muted-foreground">
+        <p class="text-sm text-muted-foreground sm:text-base">
             Drop anywhere, paste or choose files. Max {{ maxQueueSize }} images, up to {{ maxImageSizeLabel }} each.
         </p>
 
         <div class="flex flex-col gap-3 sm:flex-row sm:items-center sm:justify-between">
             <label
-                class="inline-flex items-center justify-center rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground transition-colors hover:opacity-90"
+                class="inline-flex w-full items-center justify-center rounded-md bg-primary px-4 py-2.5 text-sm font-medium text-primary-foreground transition-colors hover:opacity-90 sm:w-auto"
                 :class="disabled ? 'cursor-not-allowed opacity-60' : 'cursor-pointer'"
             >
                 Choose images
@@ -24,7 +24,7 @@
             <button
                 v-if="!uploadConfirmed"
                 type="button"
-                class="inline-flex shrink-0 items-center justify-center rounded-md bg-primary px-4 py-2 text-sm font-medium text-primary-foreground transition-colors hover:opacity-90 disabled:cursor-not-allowed disabled:opacity-60"
+                class="inline-flex w-full shrink-0 items-center justify-center rounded-md bg-primary px-4 py-2.5 text-sm font-medium text-primary-foreground transition-colors hover:opacity-90 disabled:cursor-not-allowed disabled:opacity-60 sm:w-auto"
                 :disabled="!canOpenConfigure"
                 @click="configureModalOpen = true"
             >