fix(mobile): switch to remote appVersionSource for auto-incrementing build numbers

Change `appVersionSource` from `"local"` to `"remote"` in `eas.json` so EAS
tracks build numbers on its servers. This ensures every CI build gets a
unique, ever-increasing version without needing to commit bumps back to
the repo — fixing the App Store Connect "bundle version already used"
rejection.

Also bump `ios.buildNumber` to "7" and `android.versionCode` to 7 in
`app.json` (above the previously uploaded version "6") so the remote
version initializes correctly.

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

mobile/app.json

@@ -44,7 +44,7 @@
           }
         ]
       },
-      "buildNumber": "3"
+      "buildNumber": "7"
     },
     "android": {
       "adaptiveIcon": {
@@ -71,7 +71,7 @@
           "category": ["DEFAULT"]
         }
       ],
-      "versionCode": 1
+      "versionCode": 7
     },
     "web": {
       "favicon": "./assets/favicon.png",