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/tsconfig.json

@@ -0,0 +1,8 @@
+{
+  "compilerOptions": {
+    "target": "ES2024",
+    "strict": true,
+    "alwaysStrict": true,
+    "outDir": "static"
+  }
+}