set up for deployment

backend/Dockerfile

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+# Build stage
+FROM golang:1.25.3-alpine AS builder
+
+# Install build dependencies
+RUN apk add --no-cache git ca-certificates tzdata
+
+# Set working directory
+WORKDIR /app
+
+# Copy go mod files
+COPY go.mod go.sum ./
+
+# Download dependencies
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build the application
+# CGO_ENABLED=0 for static binary, GOOS=linux for Linux compatibility
+RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -ldflags="-w -s" -o server ./cmd/server/main.go
+
+# Runtime stage
+FROM alpine:latest
+
+# Install CA certificates for HTTPS requests (OAuth)
+RUN apk --no-cache add ca-certificates tzdata
+
+# Create non-root user
+RUN addgroup -g 1000 appuser && \
+    adduser -D -u 1000 -G appuser appuser
+
+WORKDIR /app
+
+# Copy binary from builder
+COPY --from=builder /app/server .
+
+# Change ownership to non-root user
+RUN chown -R appuser:appuser /app
+
+# Switch to non-root user
+USER appuser
+
+# Expose port (Fly.io uses PORT env variable)
+EXPOSE 8080
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+    CMD wget --no-verbose --tries=1 --spider http://localhost:8080/health || exit 1
+
+# Run the application
+CMD ["./server"]