chore(mobile): add .easignore to keep native folders out of EAS builds

An untracked local android/ folder (from an earlier expo run:android)
was inflating the build archive to 365MB and, more importantly, was
making EAS Build treat the project as "bare workflow" — building that
stale native folder as-is instead of regenerating it from app.json via
Continuous Native Generation. Deleted the folder locally and excluded
it (plus ios/, node_modules, IDE state) from future archives so a
stray prebuild output can't silently make app.json changes stop taking
effect.

mobile/.easignore

@@ -0,0 +1,23 @@
+# EAS Build archive exclusions — see mobile/.gitignore for the reasoning
+# behind most of these; this file matters because EAS's archiving isn't
+# strictly limited to git-tracked files, so untracked local artifacts
+# (an accidental `expo prebuild`/`expo run:android` output, IDE state,
+# etc.) can otherwise get swept into the upload.
+
+# Local native prebuild output — regenerated fresh by EAS's Continuous
+# Native Generation from app.json on every build. Keeping this out of the
+# archive isn't just about upload size: if either folder is present, EAS
+# treats the project as "bare workflow" and builds it as-is instead of
+# regenerating from app.json, silently ignoring app.json changes.
+/android
+/ios
+
+.idea
+.expo
+.vscode
+
+# Never needed — EAS installs dependencies itself on the build worker.
+node_modules
+
+# Not part of this app.
+.git