fix: Restore all files lost during destructive rebase

A previous `git pull --rebase origin main` dropped 177 local commits,
losing 3400+ files across admin-v2, backend, studio-v2, website,
klausur-service, and many other services. The partial restore attempt
(660295e2) only recovered some files.

This commit restores all missing files from pre-rebase ref 98933f5e
while preserving post-rebase additions (night-scheduler, night-mode UI,
NightModeWidget dashboard integration).

Restored features include:
- AI Module Sidebar (FAB), OCR Labeling, OCR Compare
- GPU Dashboard, RAG Pipeline, Magic Help
- Klausur-Korrektur (8 files), Abitur-Archiv (5+ files)
- Companion, Zeugnisse-Crawler, Screen Flow
- Full backend, studio-v2, website, klausur-service
- All compliance SDKs, agent-core, voice-service
- CI/CD configs, documentation, scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

studio-v2/components/ThemeToggle.tsx

@@ -0,0 +1,46 @@
+'use client'
+
+import { useTheme } from '@/lib/ThemeContext'
+
+interface ThemeToggleProps {
+  className?: string
+}
+
+export function ThemeToggle({ className = '' }: ThemeToggleProps) {
+  const { toggleTheme, isDark } = useTheme()
+
+  return (
+    <button
+      onClick={toggleTheme}
+      className={`p-3 backdrop-blur-xl border rounded-2xl transition-all ${
+        isDark
+          ? 'bg-white/10 border-white/20 text-white hover:bg-white/20'
+          : 'bg-black/5 border-black/10 text-slate-700 hover:bg-black/10'
+      } ${className}`}
+      aria-label={isDark ? 'Switch to light mode' : 'Switch to dark mode'}
+      title={isDark ? 'Hell' : 'Dunkel'}
+    >
+      {isDark ? (
+        // Sun icon for switching to light mode
+        <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path
+            strokeLinecap="round"
+            strokeLinejoin="round"
+            strokeWidth={1.5}
+            d="M12 3v1m0 16v1m9-9h-1M4 12H3m15.364 6.364l-.707-.707M6.343 6.343l-.707-.707m12.728 0l-.707.707M6.343 17.657l-.707.707M16 12a4 4 0 11-8 0 4 4 0 018 0z"
+          />
+        </svg>
+      ) : (
+        // Moon icon for switching to dark mode
+        <svg className="w-6 h-6" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+          <path
+            strokeLinecap="round"
+            strokeLinejoin="round"
+            strokeWidth={1.5}
+            d="M20.354 15.354A9 9 0 018.646 3.646 9.003 9.003 0 0012 21a9.003 9.003 0 008.354-5.646z"
+          />
+        </svg>
+      )}
+    </button>
+  )
+}