Initial commit: React frontend (SLP Software) + AIDLC workflow docs

Co-authored-by: Junie <junie@jetbrains.com>

src/components/ThemeToggle.tsx

@@ -0,0 +1,27 @@
+import { useTheme } from '../theme/ThemeProvider';
+
+/**
+ * Visible theme switcher (requirements FR-3, Functional Design Q1/Q7).
+ * Rendered as a small icon/swatch button in the nav.
+ */
+export function ThemeToggle() {
+  const { theme, toggleTheme } = useTheme();
+  const isPurple = theme === 'purple';
+
+  return (
+    <button
+      type="button"
+      onClick={toggleTheme}
+      aria-label="Wissel kleurthema"
+      aria-pressed={isPurple}
+      data-testid="theme-toggle-button"
+      className="font-mono flex h-8 w-8 items-center justify-center rounded-full border border-line text-xs font-medium text-text transition-colors hover:border-accent-line"
+    >
+      <span
+        aria-hidden="true"
+        className="block h-4 w-4 rounded-full bg-accent"
+        data-testid="theme-toggle-swatch"
+      />
+    </button>
+  );
+}