feat: AcroForm-Fill via Claude CLI, Multi-Source, Kanagawa, Docker-Deploy

Komplettes Rework der AI-Studio-Vorlage zu einem produktiven Werkzeug fuer
deutsche AcroForm-Formulare (Reha-Antraege, Arzt-Befundberichte):

- Backend: Express spawnt headless Claude CLI ('claude -p --output-format json'
  via stdin-Pipe). Prompt enthaelt die Feldnamen als Ziel-Schema plus die
  Arbeitsregeln (Stichwortstil, feste Zeichen-Kaestchen ohne Leerzeichen,
  Vordrucke respektieren, keine geratenen Werte, nur medizinisch).
- PDF-Handling: pdfjs-dist statt pdf-lib — pdf-lib scheitert an verschluesselten
  Object-Streams in DRV-Formularen. annotationStorage + saveDocument, kein
  Flatten. Worker-Patch zur Laufzeit forciert Auto-Size und schwarze Schrift.
- Multi-Source-Upload: beliebig viele PDFs/Bilder + optional Freitext.
- Design: Kanagawa Design System (Preset aus ../kanagawa-design-system),
  Tailwind lokal gebaut statt CDN, Dark/Light-Toggle, Progress-Indicator.
- Deployment: Multi-Stage-Dockerfile, docker-compose in matrix_default-Netz,
  Claude-Credentials vom Host per Volume. PLAN.md + AGENTS.md (Alex-Schema).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

components/ThemeToggle.tsx

@@ -0,0 +1,53 @@
+import React, { useEffect, useState } from 'react';
+import { Moon, Sun } from 'lucide-react';
+
+const STORAGE_KEY = 'kng_theme';
+type Theme = 'dark' | 'light';
+
+function getSystemTheme(): Theme {
+  if (typeof window === 'undefined' || !window.matchMedia) return 'dark';
+  return window.matchMedia('(prefers-color-scheme: light)').matches
+    ? 'light'
+    : 'dark';
+}
+
+function readStored(): Theme | null {
+  try {
+    const v = localStorage.getItem(STORAGE_KEY);
+    return v === 'dark' || v === 'light' ? v : null;
+  } catch {
+    return null;
+  }
+}
+
+function applyTheme(theme: Theme) {
+  document.documentElement.setAttribute('data-theme', theme);
+}
+
+export const ThemeToggle: React.FC = () => {
+  const [theme, setTheme] = useState<Theme>(() => readStored() ?? getSystemTheme());
+
+  useEffect(() => {
+    applyTheme(theme);
+    try {
+      localStorage.setItem(STORAGE_KEY, theme);
+    } catch {
+      // localStorage nicht verfügbar — egal
+    }
+  }, [theme]);
+
+  return (
+    <button
+      onClick={() => setTheme(theme === 'dark' ? 'light' : 'dark')}
+      className="p-2 rounded-kng-md border border-kng-border bg-kng-surface hover:bg-kng-surface-hover text-kng-text-secondary hover:text-kng-text transition-colors"
+      aria-label={theme === 'dark' ? 'Zu Light-Mode wechseln' : 'Zu Dark-Mode wechseln'}
+      title={theme === 'dark' ? 'Light-Mode' : 'Dark-Mode'}
+    >
+      {theme === 'dark' ? (
+        <Sun className="w-4 h-4" />
+      ) : (
+        <Moon className="w-4 h-4" />
+      )}
+    </button>
+  );
+};