Add devenv processes for dev server and build:watch

- Add build:watch script to package.json (turbo build --watch)
- Configure devenv processes:
  - dev: runs turbo dev server
  - build-watch: runs turbo build in watch mode
- Run with `devenv up` to start all processes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

devenv.nix

@@ -15,6 +15,7 @@
   };
 
   processes = {
-    dashboard.exec = "bun run --filter @publisher/dashboard dev";
+    dev.exec = "bun run dev";
+    build-watch.exec = "bun run build:watch";
   };
 }