feat(client): add shadcn theme

- Added Nix theme
- Defaults to dark mode

Signed-off-by: Noa Virellia <noa@requiem.garden>

client/src/hooks/useTheme.ts

@@ -0,0 +1,24 @@
+import { createContext, use } from 'react';
+
+export type Theme = 'dark' | 'light' | 'system';
+
+interface ThemeProviderState {
+  theme: Theme;
+  setTheme: (theme: Theme) => void;
+}
+
+const initialState: ThemeProviderState = {
+  theme: 'system',
+  setTheme: () => null,
+};
+
+export const ThemeProviderContext = createContext<ThemeProviderState>(initialState);
+
+export function useTheme() {
+  const context = use(ThemeProviderContext);
+
+  if (context === undefined)
+    throw new Error('useTheme must be used within a ThemeProvider');
+
+  return context;
+}