Add nginx reverse proxy and environment configuration

- Add nginx.conf for proxying API requests to backend
- Update frontend Dockerfile for production build with nginx
- Move hardcoded values to .env variables in docker-compose.yml
- Add .env.example template for configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.env.example

@@ -0,0 +1,58 @@
+# ===========================================
+# Anime Quiz - Environment Configuration
+# ===========================================
+# Copy this file to .env and fill in your values
+
+# PostgreSQL Database
+POSTGRES_USER=animequiz
+POSTGRES_PASSWORD=your_secure_password_here
+POSTGRES_DB=animequiz
+
+# Database connection (for backend)
+# Format: postgresql+asyncpg://USER:PASSWORD@HOST:PORT/DB
+DATABASE_URL=postgresql+asyncpg://animequiz:your_secure_password_here@db:5432/animequiz
+
+# ===========================================
+# S3 Storage Configuration
+# ===========================================
+S3_ENDPOINT=https://s3.firstvds.ru
+S3_ACCESS_KEY=your_access_key_here
+S3_SECRET_KEY=your_secret_key_here
+S3_REGION=default
+S3_BUCKET=anime-quiz
+
+# ===========================================
+# Paths Configuration
+# ===========================================
+OUTPUT_PATH=/app/output/videos
+TEMP_PATH=/tmp/anime_quiz
+CACHE_PATH=/tmp/anime_quiz/cache
+
+# ===========================================
+# Video Settings
+# ===========================================
+SHORTS_WIDTH=1080
+SHORTS_HEIGHT=1920
+FULL_WIDTH=1920
+FULL_HEIGHT=1080
+
+# Timing (seconds)
+ANSWER_DURATION=5.0
+FINAL_SCREEN_DURATION=3.0
+AUDIO_BUFFER=1.0
+AUDIO_FADE_DURATION=0.7
+
+# ===========================================
+# Openings Downloader Settings
+# ===========================================
+DOWNLOADER_SHIKIMORI_USER_AGENT=AnimeQuiz/1.0
+DOWNLOADER_SHIKIMORI_TOKEN=your_shikimori_oauth_token_here
+DOWNLOADER_S3_STORAGE_LIMIT_BYTES=107374182400
+DOWNLOADER_DOWNLOAD_TIMEOUT_SECONDS=300
+DOWNLOADER_DEFAULT_ESTIMATED_SIZE_BYTES=6291456
+
+# ===========================================
+# Ports Configuration
+# ===========================================
+APP_PORT=5001
+DB_PORT=5003