cmd/pkgserver: move ui internal

This avoids inadvertently exporting a go package. This change also cleans up generate layout.

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

cmd/pkgserver/internal/ui/ui_full.go

@@ -0,0 +1,10 @@
+//go:build frontend
+
+package ui
+
+import "embed"
+
+//go:generate tsc
+//go:generate cp index.html style.css static
+//go:embed static
+var content embed.FS