feat: add red theme and board background modal

- Introduced a new red theme with custom color variables for a bold aesthetic.
- Updated the theme management to include the new red theme option.
- Added a BoardBackgroundModal component for managing board background settings, including image uploads and opacity controls.
- Enhanced KanbanCard and KanbanColumn components to support new background settings such as opacity and border visibility.
- Updated API client to handle saving and deleting board backgrounds.
- Refactored theme application logic to accommodate the new preview theme functionality.

apps/app/src/config/theme-options.ts

@@ -5,6 +5,7 @@ import {
   Eclipse,
   Flame,
   Ghost,
+  Heart,
   Moon,
   Radio,
   Snowflake,
@@ -85,4 +86,10 @@ export const themeOptions: ReadonlyArray<ThemeOption> = [
     Icon: Radio,
     testId: "synthwave-mode-button",
   },
+  {
+    value: "red",
+    label: "Red",
+    Icon: Heart,
+    testId: "red-mode-button",
+  },
 ];