migrate remaining admin pages to inline feedback

Replace put_flash with inline feedback for form saves:
- Media library: metadata save shows "Saved" checkmark
- Product show: storefront controls save shows "Saved" checkmark
- Newsletter campaign form: draft save shows "Saved" checkmark

Page-level outcomes (uploads, deletes, async operations) remain as
flash/banner messages — these are the correct pattern for non-form
actions.

Completes Task 4 of notification overhaul.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/berrypod_web/live/admin/media.ex

@@ -17,6 +17,7 @@ defmodule BerrypodWeb.Admin.Media do
       |> assign(:edit_form, nil)
       |> assign(:upload_alt, "")
       |> assign(:confirm_delete, false)
+      |> assign(:metadata_status, :idle)
       |> allow_upload(:media_upload,
         accept: ~w(.png .jpg .jpeg .webp .svg .gif),
         max_entries: 1,
@@ -114,7 +115,8 @@ defmodule BerrypodWeb.Admin.Media do
        |> assign(:selected_image, Map.put(image, :data, nil))
        |> assign(:selected_usages, usages)
        |> assign(:edit_form, form)
-       |> assign(:confirm_delete, false)}
+       |> assign(:confirm_delete, false)
+       |> assign(:metadata_status, :idle)}
     else
       {:noreply, socket}
     end
@@ -141,10 +143,10 @@ defmodule BerrypodWeb.Admin.Media do
          socket
          |> stream_insert(:images, updated_no_blob)
          |> assign(:selected_image, updated_no_blob)
-         |> put_flash(:info, "Metadata updated")}
+         |> assign(:metadata_status, :saved)}
 
       {:error, _changeset} ->
-        {:noreply, put_flash(socket, :error, "Failed to update metadata")}
+        {:noreply, assign(socket, :metadata_status, :error)}
     end
   end
 
@@ -398,9 +400,12 @@ defmodule BerrypodWeb.Admin.Media do
             <.input field={@edit_form[:alt]} label="Alt text" placeholder="Describe this image..." />
             <.input field={@edit_form[:caption]} label="Caption" placeholder="Optional caption..." />
             <.input field={@edit_form[:tags]} label="Tags" placeholder="hero, homepage, banner..." />
-            <button type="submit" class="admin-btn admin-btn-primary admin-btn-sm">
-              Save metadata
-            </button>
+            <div class="admin-form-actions-sm">
+              <button type="submit" class="admin-btn admin-btn-primary admin-btn-sm">
+                Save metadata
+              </button>
+              <.inline_feedback status={@metadata_status} />
+            </div>
           </.form>
 
           <%= if @selected_usages != [] do %>