feat: Add Raspberry Pi webcam capture and upload demo with install/uninstall scripts, config, and README.

demo/README.md

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+# Raspberry Pi Webcam Capture Demo
+
+Automated picture capture and upload for Raspberry Pi 3 with a USB webcam (Logitech 1080p).
+
+## Quick Setup (5 minutes)
+
+### 1. Install Required Packages
+
+```bash
+sudo apt update && sudo apt install -y fswebcam curl
+```
+
+### 2. Configure the Script
+
+```bash
+# Copy the config template
+cp picupper.conf.example picupper.conf
+
+# Edit with your settings
+nano picupper.conf
+```
+
+Update `picupper.conf` with your API key and camera settings.
+
+### 3. Install & Enable
+
+```bash
+# Make scripts executable
+chmod +x capture-upload.sh install.sh
+
+# Run installer (sets up cron job)
+./install.sh
+```
+
+That's it! Your Pi will now capture and upload one picture per minute.
+
+---
+
+## Files Included
+
+| File | Purpose |
+|------|---------|
+| `capture-upload.sh` | Main script - captures photo and uploads |
+| `picupper.conf.example` | Configuration template |
+| `install.sh` | Installer script (sets up cron) |
+| `uninstall.sh` | Removes cron job |
+
+## Configuration Options
+
+Edit `picupper.conf`:
+
+```bash
+# PicUpper server URL
+API_URL="https://dev.seedheads.de/picUploadApi/upload"
+
+# Your API key (from server admin)
+API_KEY="your-api-key-here"
+
+# Camera identifier (unique name for this Pi)
+CAMERA_ID="rpi-webcam-1"
+
+# Resolution (1920x1080 for full HD)
+RESOLUTION="1920x1080"
+
+# Video device (usually /dev/video0)
+VIDEO_DEVICE="/dev/video0"
+```
+
+## Manual Testing
+
+```bash
+# Test capture only (saves to /tmp)
+./capture-upload.sh --test
+
+# Run full capture and upload once
+./capture-upload.sh
+```
+
+## Troubleshooting
+
+### Check if webcam is detected
+
+```bash
+ls /dev/video*
+v4l2-ctl --list-devices
+```
+
+### Test capture manually
+
+```bash
+fswebcam -d /dev/video0 -r 1920x1080 --no-banner test.jpg
+```
+
+### Check logs
+
+```bash
+# View recent capture logs
+tail -f /var/log/picupper.log
+```
+
+### Common Issues
+
+| Problem | Solution |
+|---------|----------|
+| "No video device" | Replug USB webcam, check `dmesg` |
+| "Permission denied" | Add user to video group: `sudo usermod -aG video $USER` |
+| "Upload failed" | Check API key and network connection |
+
+## Changing Capture Frequency
+
+Default is 1 picture per minute. To change:
+
+```bash
+# Edit cron job
+crontab -e
+```
+
+Examples:
+- Every 5 minutes: `*/5 * * * * /home/pi/picupper-demo/capture-upload.sh`
+- Every 30 seconds: Use the included systemd timer (see advanced setup)
+
+## Hardware Requirements
+
+- Raspberry Pi 3 (any model)
+- USB webcam (Logitech C920/C922/C270 recommended)
+- SD card with Raspberry Pi OS
+- Network connection (WiFi or Ethernet)
+
+## Network Notes
+
+The script retries failed uploads and logs all attempts. If your Pi loses network, captures continue and uploads resume when connectivity returns.