feat: add dark mode support, accordion UI, and current combination display

- Update Theme Studio sidebar to use DaisyUI theme-aware classes for dark mode
- Convert Customise accordion to native details/summary elements for proper interaction
- Add "Current combination" card showing active theme settings
- Add SVG recolorer for logo color customization
- Add image controller for serving uploaded images
- Implement header background image controls (zoom, position)
- Add toggle_customise event handler to preserve accordion state across re-renders

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

lib/simpleshop_theme_web/controllers/image_controller.ex

@@ -0,0 +1,93 @@
+defmodule SimpleshopThemeWeb.ImageController do
+  use SimpleshopThemeWeb, :controller
+
+  alias SimpleshopTheme.Media
+  alias SimpleshopTheme.Media.SVGRecolorer
+
+  @doc """
+  Serves an image from the database by ID.
+
+  Images are served with aggressive caching headers since they are
+  immutable once uploaded.
+  """
+  def show(conn, %{"id" => id}) do
+    case Media.get_image(id) do
+      nil ->
+        send_resp(conn, 404, "Image not found")
+
+      image ->
+        conn
+        |> put_resp_content_type(image.content_type)
+        |> put_resp_header("cache-control", "public, max-age=31536000, immutable")
+        |> put_resp_header("etag", ~s("#{image.id}"))
+        |> send_resp(200, image.data)
+    end
+  end
+
+  @doc """
+  Serves a thumbnail of an image if available, otherwise falls back to full image.
+  """
+  def thumbnail(conn, %{"id" => id}) do
+    case Media.get_image(id) do
+      nil ->
+        send_resp(conn, 404, "Image not found")
+
+      %{thumbnail_data: thumbnail_data} = image when not is_nil(thumbnail_data) ->
+        conn
+        |> put_resp_content_type("image/jpeg")
+        |> put_resp_header("cache-control", "public, max-age=31536000, immutable")
+        |> put_resp_header("etag", ~s("#{image.id}-thumb"))
+        |> send_resp(200, thumbnail_data)
+
+      image ->
+        conn
+        |> put_resp_content_type(image.content_type)
+        |> put_resp_header("cache-control", "public, max-age=31536000, immutable")
+        |> put_resp_header("etag", ~s("#{image.id}"))
+        |> send_resp(200, image.data)
+    end
+  end
+
+  @doc """
+  Serves an SVG image recolored with the specified color.
+
+  The color should be a hex color code (with or without the leading #).
+  Only works with SVG images.
+  """
+  def recolored_svg(conn, %{"id" => id, "color" => color}) do
+    clean_color = normalize_color(color)
+
+    with true <- SVGRecolorer.valid_hex_color?(clean_color),
+         %{is_svg: true, svg_content: svg} when not is_nil(svg) <- Media.get_image(id) do
+      recolored = SVGRecolorer.recolor(svg, clean_color)
+
+      conn
+      |> put_resp_content_type("image/svg+xml")
+      |> put_resp_header("cache-control", "public, max-age=3600")
+      |> put_resp_header("etag", ~s("#{id}-#{clean_color}"))
+      |> send_resp(200, recolored)
+    else
+      false ->
+        send_resp(conn, 400, "Invalid color format")
+
+      nil ->
+        send_resp(conn, 404, "Image not found")
+
+      %{is_svg: false} ->
+        send_resp(conn, 400, "Image is not an SVG")
+
+      %{svg_content: nil} ->
+        send_resp(conn, 400, "SVG content not available")
+    end
+  end
+
+  defp normalize_color(color) do
+    color = String.trim(color)
+
+    if String.starts_with?(color, "#") do
+      color
+    else
+      "#" <> color
+    end
+  end
+end