replace admin rail with unified bottom sheet editor

- add editor sheet component anchored bottom (mobile) / right (desktop)
- admin cog moves to header, always visible for admins
- remove Done button from editor header, keep only Save
- add editor_at_defaults tracking to disable Reset when at defaults
- sheet collapses on click outside or Escape, stays in edit mode
- dirty indicator + beforeunload warning for unsaved changes
- keyboard shortcuts: Ctrl+Z undo, Ctrl+Shift+Z redo
- WCAG compliant: aria-expanded, live region, focus management

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

lib/berrypod_web/components/core_components.ex

@@ -47,7 +47,7 @@ defmodule BerrypodWeb.CoreComponents do
       id={@id}
       phx-click={JS.push("lv:clear-flash", value: %{key: @kind}) |> hide("##{@id}")}
       role="alert"
-      class="admin-toast"
+      class="admin-banner"
       {@rest}
     >
       <div class={[
@@ -70,6 +70,39 @@ defmodule BerrypodWeb.CoreComponents do
     """
   end
 
+  @doc """
+  Renders inline status feedback next to a button or form section.
+
+  ## Examples
+
+      <.inline_feedback status={@save_status} />
+      <.inline_feedback status={@save_status} message={@save_error} />
+  """
+  attr :status, :atom, values: [:idle, :saving, :saved, :error], default: :idle
+  attr :message, :string, default: nil
+
+  def inline_feedback(assigns) do
+    ~H"""
+    <span
+      :if={@status != :idle}
+      class={["admin-inline-feedback", "admin-inline-feedback-#{@status}"]}
+      role={@status == :error && "alert"}
+    >
+      <.icon :if={@status == :saving} name="hero-arrow-path" class="size-4 motion-safe:animate-spin" />
+      <.icon :if={@status == :saved} name="hero-check" class="size-4" />
+      <.icon :if={@status == :error} name="hero-exclamation-circle" class="size-4" />
+      <span>{feedback_text(@status, @message)}</span>
+    </span>
+    """
+  end
+
+  defp feedback_text(:saving, _), do: "Saving..."
+  defp feedback_text(:saved, nil), do: "Saved"
+  defp feedback_text(:saved, msg), do: msg
+  defp feedback_text(:error, nil), do: "Something went wrong"
+  defp feedback_text(:error, msg), do: msg
+  defp feedback_text(:idle, _), do: nil
+
   @doc """
   Renders a button with navigation support.