chore: make clean and docker cleanup

- adds 'make clean' that removes artifacts
- improves ux when working with docker, especially when image is missing
- 'make' only builds the binary, kubo logic needs to be explicitly
  called

Makefile

@@ -23,7 +23,7 @@ provision-cargateway: ./fixtures.car
 
 provision-kubo:
 	find ./fixtures -name '*.car' -exec ipfs dag import --stats --pin-roots=false {} \;
-	find ./fixtures -name '*.ipns-record' -exec sh -c 'ipfs routing put --allow-offline /ipns/$$(basename -s .ipns-record "{}") "{}"' \;
+	find ./fixtures -name '*.ipns-record' -exec sh -c 'ipfs routing put --offline --allow-offline /ipns/$$(basename -s .ipns-record "{}") "{}"' \;
 
 # tools
 fixtures.car: gateway-conformance