added pi zero backend for wrapping gpsd

pi/backend/README.md

@@ -0,0 +1,71 @@
+# Backend
+
+Python GPS service for Smart Serow. Connects to `gpsd`, buffers positions, exposes HTTP API.
+
+## Setup
+
+```bash
+# Install uv if you haven't
+curl -LsSf https://astral.sh/uv/install.sh | sh
+
+# Install dependencies
+cd pi/backend
+uv sync
+```
+
+## Run
+
+```bash
+uv run python main.py
+```
+
+Or for development:
+```bash
+uv run flask --app main run --host 0.0.0.0 --port 5000 --reload
+```
+
+## API
+
+| Endpoint | Description |
+|----------|-------------|
+| `GET /health` | Health check, shows gpsd connection status |
+| `GET /gps` | Latest GPS fix (lat, lon, alt, speed, track) |
+| `GET /gps/history` | Last 100 buffered positions |
+
+## Test from SSH
+
+```bash
+curl http://localhost:5000/health
+curl http://localhost:5000/gps
+curl http://localhost:5000/gps/history | jq
+```
+
+## gpsd Setup (Pi)
+
+```bash
+# Install
+sudo apt install gpsd gpsd-clients
+
+# Configure (edit DEVICES to match your GPS serial port)
+sudo nano /etc/default/gpsd
+
+# Example /etc/default/gpsd:
+# DEVICES="/dev/ttyUSB0"
+# GPSD_OPTIONS="-n"
+# START_DAEMON="true"
+
+# Restart
+sudo systemctl restart gpsd
+
+# Test gpsd directly
+gpsmon
+cgps -s
+```
+
+## Stub Mode
+
+If `gpsdclient` isn't installed or gpsd isn't running, the service generates fake GPS data for UI testing.
+
+## Deploy
+
+TODO: Add to `scripts/deploy.py` as second target + systemd service.