Add AgriMesh demo for multi-hop field reading store-and-forward

[Ankush523]

Summary

• Adds apps/agrimesh, the agriculture vertical demo: field readings are logged on a field collector, carried over Bluetooth mesh (optional relay worker when plot and office are out of direct BLE range), and accumulated on an office-edge host ledger.
• Mock farm system sync uses stable readingId keys with visible duplicates dropped on repeat upload (same honesty pattern as OutageNet HQ / Event Floor platform sync).
• Presenter strip shows readings count, synced ids, farm row total, and dupe counter; field UI shows pending hop vs ledger confirmation.
• Reuses @offline-app-examples/mesh (useNearbyRoom + useMeshRelay); no new mesh package APIs.
• CI: Android/iOS matrix entries for agrimesh; root README + docs/DEMO_APPS_PLAN.md updated.

Test plan

• pnpm install --frozen-lockfile && pnpm typecheck && pnpm lint && pnpm test
• 3 phones: Office edge → Start; Relay → Start (between field and office); Field collector → Start → log North ridge moisture → office shows reading.
• Office Sync to farm system (mock) twice → second sync increments dupes dropped.
• iOS: cd apps/agrimesh && bundle install && cd ios && bundle exec pod install (retry loop if null-byte flake); run on device with Metro.
• Android: pnpm --filter @offline-app-examples/agrimesh android on device.
• (Follow-up) Record apps/agrimesh/demo.gif for catalogue embed.

Notes

• Completes the four-app demo plan (OutageNet, YardGate, Event Floor, AgriMesh).
• Physical devices + Bluetooth required for mesh; simulators UI-only.