Refactor Docker setup and enhance development environment

- Updated docker-compose.dev.yml to use Dockerfile.dev for backend builds and added HOST environment variable for frontend.
- Introduced Dockerfile.dev for streamlined backend development with Go.
- Enhanced development documentation to reflect changes in local setup and API proxying.
- Removed outdated frontend Dockerfile and adjusted frontend configuration for improved development experience.

Dockerfile.dev

@@ -0,0 +1,13 @@
+FROM golang:1.21-alpine
+
+WORKDIR /hnh-map
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN go build -o hnh-map ./cmd/hnh-map
+
+EXPOSE 3080
+
+CMD ["/hnh-map/hnh-map", "-grids=/map"]