Rename product to dockmv (container, image, module, env vars)

Container/image/service name, Go module path, CLI binary name, and
DOCKER_MIGRATE_* env vars still used the old working name; the project
is branded DockMV everywhere else (README, logo, Gitea repo).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -18,22 +18,22 @@ COPY --from=ui /src/internal/webui/dist ./internal/webui/dist
 # artifact be copied onto a bare-metal host.
 RUN CGO_ENABLED=0 go build -trimpath \
       -ldflags "-s -w -X main.version=${VERSION}" \
-      -o /out/docker-migrate .
+      -o /out/dockmv .
 
 FROM alpine:3.22
 RUN apk add --no-cache ca-certificates tzdata && \
     adduser -D -u 10001 migrate
-COPY --from=build /out/docker-migrate /usr/local/bin/docker-migrate
+COPY --from=build /out/dockmv /usr/local/bin/dockmv
 
 # The container talks to the Docker socket mounted from the host, which is
 # owned by root:docker. It therefore runs as root by default; set --user to
 # override when the socket permissions on your host allow it.
-ENV DOCKER_MIGRATE_DATA=/data
+ENV DOCKMV_DATA=/data
 VOLUME ["/data"]
 EXPOSE 8080
 
 HEALTHCHECK --interval=30s --timeout=5s --start-period=5s \
   CMD wget -qO- http://127.0.0.1:8080/api/health >/dev/null || exit 1
 
-ENTRYPOINT ["docker-migrate"]
+ENTRYPOINT ["dockmv"]
 CMD ["serve", "--addr", "0.0.0.0:8080"]