Upgrade the step apps from Expo SDK 49 to a supported SDK (and React Native 0.82)

Dependabot has open PRs moving the workshop apps from Expo SDK 49.0.16 to 54.0.32 (#90, #82, #91, #92, #88) and React Native 0.72.6 to 0.82.1 (#72, #71). These were deliberately left out of the consolidation PR #93, which took only the lockfile-level security updates.

Why it needs a human:

• Expo 49 → 54 is five SDK generations. It pulls react 18 → 19, @types/react, react-native-reanimated, react-native-safe-area-context and the babel config along with it, and expo install --fix decides those versions per SDK.
• step0–step5 define no build or test script (only android/ios/start/web), so there is no automated signal that an upgrade is safe — each step has to be run on a simulator or device.
• The workshop content teaches against SDK 49 APIs; the step-by-step material likely needs updating alongside the bump.

Suggested approach: upgrade one step at a time with npx expo install --fix, run each step app, then update the slides where the API changed. Expo SDK 49 is well past its support window, so this is worth scheduling rather than leaving to Dependabot.

Related: #93 (consolidation PR that covers everything else), and the seven Dependabot PRs listed above, which are intentionally still open.

Start with the step0–step5 apps and run npx expo install --fix in each, then inspect the workshop slides for SDK-dependent APIs. Run every step app on a simulator or device, update the affected material, and confirm all six apps work on the supported Expo and React Native versions.