Adds a dedicated dev container under .devcontainer/mobile/ following the
monorepo multi-container pattern. Includes a multi-stage Dockerfile with
Android SDK (platform 36) and Flutter 3.29.2, a devcontainer.json with
Dart/Flutter VS Code extensions, and an on-create script that configures
Flutter for Android-only development and installs project dependencies.
https://claude.ai/code/session_013F3TXesccdf2ta5qwykPtt
