Initial commit: Deklinationstrainer German declension trainer

Vite + React app for daily German declension practice with
localStorage-backed progress. Includes Coolify deploy instructions.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

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+# Deklinationstrainer
+
+A daily-practice German declension trainer. Self-hosted so your progress actually saves.
+
+## Deploy to Coolify
+
+### One-time setup
+
+1. Push these files to a git repo (GitHub / Gitea / whatever Coolify is connected to).
+
+2. In Coolify, create a new **Application**:
+   - Source: your git repo
+   - Build pack: **Nixpacks** (auto-detects Vite) or **Static**
+   - Build command: `npm run build`
+   - Publish directory: `dist`
+   - Port: not needed for static output (Coolify serves it directly)
+
+3. Add a domain (e.g. `deklination.yourdomain.com`). Coolify provisions HTTPS via Caddy/Traefik automatically.
+
+4. Deploy. Visit the URL on any device.
+
+### Local dev
+
+```bash
+npm install
+npm run dev    # http://localhost:5173
+npm run build  # outputs to ./dist
+```
+
+## On iPhone
+
+Open the URL in Safari, tap Share → **Add to Home Screen**. It opens fullscreen like a native app, and progress saves in localStorage across reboots, sessions, and app closes.
+
+## Storage
+
+The app tries `window.storage` first (Claude artifact environment), then falls back to `localStorage`. When self-hosted, only localStorage runs, which iOS Safari persists reliably.
+
+To wipe progress: open browser devtools → Application → Local Storage → delete the `gd-v10` key. Or on iPhone: Settings → Safari → Advanced → Website Data → search your domain → delete.