fix content image double-suffix, clean up page defaults and editor UX

- Fix resolve_content_image returning base path (not full URL) so
  responsive_image doesn't double-append width/extension
- Remove legacy image fields (image_src, image_alt, image_url) from
  block settings schemas
- Remove demo/mockup fallbacks from renderer and defaults — blank
  fields stay blank instead of showing preview content
- Replace demo text in defaults with instructional placeholders that
  guide new shop owners
- Remove redundant X button from editor sidebar, add unsaved-changes
  confirmation to Done button
- Fix block card name overflow on mobile (display: block, flex-wrap)
- Add onboarding UX improvement plan (10 tasks)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test/berrypod_web/live/shop/content_test.exs

@@ -14,14 +14,14 @@ defmodule BerrypodWeb.Shop.ContentTest do
     test "renders about page", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/about")
 
-      assert html =~ "About the studio"
-      assert html =~ "sample about page"
+      assert html =~ "About us"
+      assert html =~ "Tell your customers who you are"
     end
 
-    test "displays about image", %{conn: conn} do
+    test "displays about content body", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/about")
 
-      assert html =~ "night-sky-blanket"
+      assert html =~ "placeholder text"
     end
   end
 

test/berrypod_web/live/shop/home_test.exs

@@ -30,7 +30,7 @@ defmodule BerrypodWeb.Shop.HomeTest do
     test "renders the home page", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/")
 
-      assert html =~ "Original designs, printed on demand"
+      assert html =~ "Your headline goes here"
     end
 
     test "renders hero section with CTA", %{conn: conn} do
@@ -55,8 +55,8 @@ defmodule BerrypodWeb.Shop.HomeTest do
     test "renders image and text section", %{conn: conn} do
       {:ok, _view, html} = live(conn, ~p"/")
 
-      assert html =~ "Made with passion, printed with care"
-      assert html =~ "Learn more about the studio"
+      assert html =~ "Your story in a nutshell"
+      assert html =~ "Read more about us"
     end
 
     test "renders header with shop name", %{conn: conn} do