refactor(media): use asset-centric storage key layout

apps/admin/src/components/media/media-upload-form.tsx

@@ -44,10 +44,15 @@ export function MediaUploadForm() {
 
       const payload = (await response.json().catch(() => null)) as {
         notice?: string
+        provider?: "s3" | "local"
+        warning?: string
       } | null
 
       const notice = payload?.notice ?? "Media uploaded."
-      window.location.href = `/media?notice=${encodeURIComponent(notice)}`
+      const provider = payload?.provider ?? "local"
+      const warning = payload?.warning
+      const warningQuery = warning ? `&warning=${encodeURIComponent(warning)}` : ""
+      window.location.href = `/media?notice=${encodeURIComponent(notice)}&uploadedVia=${encodeURIComponent(provider)}${warningQuery}`
     } catch {
       setError("Upload request failed. Please retry.")
     } finally {
@@ -68,8 +73,7 @@ export function MediaUploadForm() {
           <span className="text-xs text-neutral-600">Title</span>
           <input
             name="title"
-            required
-            minLength={1}
+            placeholder="Optional (defaults to file name)"
             className="w-full rounded border border-neutral-300 px-3 py-2 text-sm"
           />
         </label>