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>

mix.exs

@@ -67,7 +67,8 @@ defmodule SimpleshopTheme.MixProject do
       {:jason, "~> 1.2"},
       {:dns_cluster, "~> 0.2.0"},
       {:bandit, "~> 1.5"},
-      {:tidewave, "~> 0.5", only: :dev}
+      {:tidewave, "~> 0.5", only: :dev},
+      {:image, "~> 0.54"}
     ]
   end