feat: implement core Go application with web server

- Add Go modules with required dependencies (Gin, UUID, JWT, etc.)
- Implement main web server with landing page endpoint
- Add comprehensive API endpoints for health and status
- Include proper error handling and request validation
- Set up CORS middleware and security headers

output/Dockerfile.landing

@@ -0,0 +1,53 @@
+# Build stage
+FROM golang:1.21-alpine AS builder
+
+WORKDIR /app
+
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY cmd/landing_main.go ./
+COPY web/ ./web/
+
+# Build the application
+RUN CGO_ENABLED=0 GOOS=linux go build -o landing-app landing_main.go
+
+# Final stage
+FROM alpine:latest
+
+# Install runtime dependencies
+RUN apk --no-cache add ca-certificates tzdata curl
+
+# Create non-root user
+RUN addgroup -g 1001 -S ydn && \
+    adduser -u 1001 -S ydn -G ydn
+
+# Set working directory
+WORKDIR /app
+
+# Copy binary from builder stage
+COPY --from=builder /app/landing-app .
+
+# Copy web assets
+COPY --from=builder /app/web ./web
+
+# Create necessary directories
+RUN mkdir -p logs configs
+
+# Change ownership
+RUN chown -R ydn:ydn /app
+
+# Switch to non-root user
+USER ydn
+
+# Expose port
+EXPOSE 8080
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=10s --start-period=5s --retries=3 \
+    CMD curl -f http://localhost:8080/health || exit 1
+
+# Run the application
+CMD ["./landing-app"]