fix: gateway install uses Gitea registry instead of npmjs

- Switch all @mosaicstack/gateway refs to @mosaic/gateway
- Install from Gitea registry (git.mosaicstack.dev)
- Remove duplicate entry resolution (was checking both package names)
- Bump @mosaic/mosaic and @mosaic/cli to 0.0.12

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaic/mosaic",
-  "version": "0.0.11",
+  "version": "0.0.12",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaic/mosaic-stack.git",