Move app-specific config from packages/app into root app-config.yaml

The example app (packages/app) had a separate app-config.yaml that was
loaded via --config flags in the start script. This moves the NFS
configuration (routes, pluginOverrides, extensions) into the root
app-config.yaml and removes the --config flags so the app uses the
default config resolution.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

packages/app/package.json

@@ -19,7 +19,7 @@
     "build": "backstage-cli package build",
     "clean": "backstage-cli package clean",
     "lint": "backstage-cli package lint",
-    "start": "backstage-cli package start --config ../../app-config.yaml --config app-config.yaml",
+    "start": "backstage-cli package start",
     "test": "backstage-cli package test"
   },
   "browserslist": {