feat: v1.1.0 - Docker, i18n, setup wizard, rate limiting, OpenAPI

New features:
- Docker support (Dockerfile + docker-compose.yml)
- GitHub Actions CI pipeline (PHP lint, JS lint, Docker build, i18n validation)
- Internationalization system with 3 languages (it, en, de) and 347 translation keys
- First-run setup wizard (4-step configuration)
- File-based API rate limiting (120/15/5 req/min tiers)
- OpenAPI 3.1.0 specification for all 43 API endpoints
- CONTRIBUTING.md with translation and development guide
- Screenshots directory placeholder

Modified:
- README.md: Docker badges, install instructions, translations section
- api/index.php: rate limiting middleware
- assets/js/app.js: i18n system, setup wizard, t() function
- assets/css/style.css: setup wizard styles
- index.html: data-i18n attributes, setup wizard overlay, language settings
- .gitignore: rate_limits exclusion

assets/img/screenshots/README.md

@@ -0,0 +1,31 @@
+# Screenshots
+
+Add screenshots here to showcase the app in the README.
+
+## Recommended screenshots
+
+Take screenshots of these pages for the README `Screenshots` section:
+
+1. **dashboard.png** — Main dashboard with stats cards and expiry alerts
+2. **inventory.png** — Inventory list with product cards
+3. **scan.png** — Barcode scanning page
+4. **recipe.png** — Generated recipe with cooking mode
+5. **shopping.png** — Shopping list with smart predictions
+6. **chat.png** — Gemini Chef AI conversation
+7. **settings.png** — Settings page
+8. **setup.png** — First-run setup wizard
+
+## How to add
+
+1. Take screenshots on a mobile device or using Chrome DevTools device emulation
+2. Recommended size: 375×812 (iPhone X viewport)
+3. Save as PNG with descriptive names
+4. Update the README.md `## Screenshots` section to reference them:
+
+```markdown
+## Screenshots
+
+| Dashboard | Inventory | Scan |
+|:-:|:-:|:-:|
+| ![Dashboard](assets/img/screenshots/dashboard.png) | ![Inventory](assets/img/screenshots/inventory.png) | ![Scan](assets/img/screenshots/scan.png) |
+```