Add Docker deployment support

- Create Dockerfile with multi-stage build for optimized image size
- Add GitHub Actions workflow for automatic image publishing to ghcr.io
- Add PORT and HOST fallback defaults in config (8080 and 0.0.0.0)
- Update README with Docker Compose installation instructions

Dockerfile

@@ -0,0 +1,22 @@
+FROM golang:1.24-alpine AS builder
+
+RUN apk add --no-cache gcc musl-dev sqlite-dev
+
+WORKDIR /app
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=1 GOOS=linux go build -a -installsuffix cgo -o apocapoc-api cmd/api/main.go
+
+FROM alpine:latest
+RUN apk --no-cache add ca-certificates sqlite-libs
+
+WORKDIR /root/
+
+COPY --from=builder /app/apocapoc-api .
+
+EXPOSE 8080
+
+CMD ["./apocapoc-api"]