cmd/pkgserver: move API implementation to package

For moving into cmd/mbf.

Signed-off-by: Ophestra <cat@gensokyo.uk>

.gitignore

@@ -7,7 +7,7 @@
 
 # go generate
 /cmd/hakurei/LICENSE
-/cmd/pkgserver/internal/ui/static
+/cmd/pkgserver/internal/pkgserver/ui/static
 /internal/pkg/testdata/testtool
 /internal/rosa/hakurei_current.tar.gz