Dual-Platform Hiking Navigation App

I’m building a Hiking Companion app for one specific region to start—a neat, scalable tool for a local community of tourists and residents. Users ask in plain language (“family‑friendly hikes under 8 km”, “below 1,000 m and ends near a BBQ”), get smart results, see them on a map, and track themselves. I also want user‑editable entries (“found a BBQ here—photo attached!”) to grow a community-sourced layer.

MUST‑HAVE MVP (fully functional mobile app)
- Mobile app (React Native or Flutter) for iOS & Android.
- Map & GPS (Mapbox/MapLibre, online only): show routes, user position, simple on‑route indicator.
- Conversational search → deterministic filters (distance, elevation gain, altitude ceiling, loop, difficulty, POI at end like BBQ). No raw LLM‑to‑SQL.
- Geospatial backend (PostgreSQL + PostGIS or equivalent) with REST/GraphQL APIs.
- Data import: one‑off ingestion from open sources (e.g., OSM + elevation model) with a manual/biannual refresh path, not continuous syncing.
- User-generated POIs: allow users to add/edit spots with photos + text; minimal moderation/workflow.
- Basics: favourites/saved hikes, license/attribution compliance, handover docs & source code.

Longer-term opportunities
- Offline vector tiles & routing, better on-route detection.
- Automated data updates (OSM diffs, closures/hazard feeds).
- Rich community features (reputation, review/merge queue).
- Extra activity layers (e.g., skiing) using the same logic.
- Smarter recommendations / personalization.
- Admin console, analytics, A/B flags, etc.

If this is your jam, tell me:
- Can you cover both backend + frontend, or just one side?
- Any similar projects (PostGIS/OSM/Mapbox, chat-to-filters)?
- Your proposed stack & approach (esp. NL → filters).
- Timeline + tentative (ideally fixed) price, and post-launch maintenance rate.