chore: .npmrc use ${GITEA_NPM_HOST}:3300 instead of hardcoded localhost

Enables NETWORK-aware Gitea registry resolution:
- NETWORK=corp → localhost (local Gitea)
- NETWORK=home → Azure VM host (from ~/.gitea_vm_host)

switch-network.sh in common-plat sets GITEA_NPM_HOST accordingly.
Matches existing .npmrc.docker pattern used during Docker builds.

.npmrc

@@ -1,3 +1,3 @@
-@bytelyst:registry=http://localhost:3300/api/packages/bytelyst/npm/
-//localhost:3300/api/packages/bytelyst/npm/:_authToken=${GITEA_NPM_TOKEN}
+@bytelyst:registry=http://${GITEA_NPM_HOST}:3300/api/packages/bytelyst/npm/
+//${GITEA_NPM_HOST}:3300/api/packages/bytelyst/npm/:_authToken=${GITEA_NPM_TOKEN}
 strict-ssl=false