move branding settings from Theme tab to Site tab

- Add branding_editor component to site_editor.ex with:
  - Shop name input
  - Show shop name / Show logo toggles
  - Logo upload (size slider, SVG recolor, color picker)
  - Header background toggle and upload (zoom, position sliders)
- Add site_ prefixed event handlers in page_editor_hook.ex:
  - site_update_branding, site_toggle_branding, site_update_color
  - site_remove_logo and site_remove_header (delegate to theme handlers)
- Remove branding sections from theme_editor.ex:
  - Deleted shop_name_input, branding_section, logo/header upload sections
- Theme tab now shows only: preset grid, accent colours, customise accordion

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

lib/berrypod_web/page_editor_hook.ex

@@ -1127,6 +1127,63 @@ defmodule BerrypodWeb.PageEditorHook do
     {:halt, socket}
   end
 
+  # ── Site branding events (route to theme state) ─────────────────────
+
+  # Handle shop name and theme branding settings from Site tab
+  defp handle_site_action("update_branding", %{"field" => "site_name"} = params, socket) do
+    # Site name updates Settings immediately (same as theme tab)
+    value = params["site_name"]
+
+    if value do
+      Settings.put_setting("site_name", value, "string")
+      {:halt, assign(socket, :site_name, value)}
+    else
+      {:halt, socket}
+    end
+  end
+
+  defp handle_site_action("update_branding", %{"field" => field} = params, socket) do
+    # Route branding setting changes to theme state
+    value = params[field] || params["setting_value"]
+
+    if value do
+      field_atom = String.to_existing_atom(field)
+      update_theme_setting(socket, %{field_atom => value}, field)
+    else
+      {:halt, socket}
+    end
+  end
+
+  defp handle_site_action("toggle_branding", %{"field" => field}, socket) do
+    # Route toggle to theme state (same logic as theme_toggle_setting)
+    field_atom = String.to_existing_atom(field)
+    current_value = Map.get(socket.assigns.theme_editor_settings, field_atom)
+    new_value = !current_value
+
+    # Prevent turning off show_site_name when there's no logo
+    if field_atom == :show_site_name && new_value == false && !has_valid_logo?(socket) do
+      {:halt, socket}
+    else
+      update_theme_setting(socket, %{field_atom => new_value}, field)
+    end
+  end
+
+  defp handle_site_action("update_color", %{"field" => field, "value" => value}, socket) do
+    # Route color updates to theme state
+    field_atom = String.to_existing_atom(field)
+    update_theme_setting(socket, %{field_atom => value}, field)
+  end
+
+  defp handle_site_action("remove_logo", _params, socket) do
+    # Delegate to theme action handler
+    handle_theme_action("remove_logo", %{}, socket)
+  end
+
+  defp handle_site_action("remove_header", _params, socket) do
+    # Delegate to theme action handler
+    handle_theme_action("remove_header", %{}, socket)
+  end
+
   # Catch-all for unknown site actions
   defp handle_site_action(_action, _params, socket), do: {:halt, socket}