chore: rename app to OpenNotes

[markm39]

Summary

• rename the public app, package metadata, docs, and in-app copy to OpenNotes
• rename native iOS/Android app identifiers, schemes, package paths, and project files
• migrate local AsyncStorage metadata/tool keys from the previous namespace to the OpenNotes namespace

Verification

• npm run typecheck
• npx expo config --type public
• pod install
• git diff --check
• rg check for old app name outside ignored/generated folders
• npm audit --omit=dev --audit-level=high

Notes

• Did not run a full native device build in this session.
• npm audit still reports moderate Expo/PostCSS advisories that require a breaking Expo major upgrade to auto-fix.