feat: add Docker deployment configuration

- Add multi-stage Dockerfile for static build
- Add nginx configuration with COOP/COEP headers for FFmpeg.wasm
- Add .dockerignore for optimized builds
- Enable SharedArrayBuffer support via security headers

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

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

Dockerfile

@@ -0,0 +1,53 @@
+# Multi-stage Dockerfile for Next.js 16 static export
+
+# Stage 1: Dependencies
+FROM node:22-alpine AS deps
+RUN apk add --no-cache libc6-compat
+WORKDIR /app
+
+# Install pnpm
+RUN corepack enable && corepack prepare pnpm@latest --activate
+
+# Copy package files
+COPY package.json pnpm-lock.yaml ./
+
+# Install dependencies
+RUN pnpm install --frozen-lockfile
+
+# Stage 2: Builder
+FROM node:22-alpine AS builder
+WORKDIR /app
+
+# Install pnpm
+RUN corepack enable && corepack prepare pnpm@latest --activate
+
+# Copy dependencies from deps stage
+COPY --from=deps /app/node_modules ./node_modules
+
+# Copy source code
+COPY . .
+
+# Build the application (static export)
+RUN pnpm build
+
+# Stage 3: Runner (serve static files)
+FROM nginx:alpine AS runner
+
+# Install curl for health check
+RUN apk add --no-cache curl
+
+# Copy custom nginx config
+COPY --from=builder /app/nginx.conf /etc/nginx/nginx.conf
+
+# Copy static files from build
+COPY --from=builder /app/out /usr/share/nginx/html
+
+# Expose port 80
+EXPOSE 80
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+  CMD curl -f http://localhost/ || exit 1
+
+# Start nginx
+CMD ["nginx", "-g", "daemon off;"]