rpi3-camera-streamer-fullhd-or-video-endpoint-broken

# Raspberry Pi 3 + camera-streamer: /video, /video*, /webrtc endpoints not working

## Symptoms
- `/stream` endpoint works fine (MJPEG)
- `/video`, `/video.mp4`, `/video.mkv` endpoints return errors
- `/webrtc` endpoint not working
- USB webcam connected, camera-streamer running
- Switching to `resolution: 1920x1080` breaks even MJPEG, returning to 720p fixes /stream

## Root Cause
RPi 3 has insufficient GPU memory for H264 hardware encoding of USB camera streams.

## Solution

### 1. Check current GPU memory:
```bash
vcgencmd get_mem gpu
# If < 128MB, needs fixing
```

### 2. Edit config safely:
```bash
sudo cp /boot/firmware/config.txt /boot/firmware/config.txt.backup  # backup first
sudo nano /boot/firmware/config.txt
```

### 3. Add GPU memory setting:
**Before any section in `[]`** (no section):
```ini
gpu_mem=128
```

**Note:** Putting it in `[all]` section didn't work for me, maybe because I tried with 256MB first.

### 4. Reboot and verify:
```bash
sudo reboot
vcgencmd get_mem gpu  # Should show 128M
```

## ⚠️ Safety Notes
- If something goes wrong, be ready with PC and card reader to edit config.txt
- Don't use values > 256MB on RPi 3

## 🧪 Test endpoints after fix:
```bash
# These should now work:
curl http://localhost:8080/video.mp4
curl http://localhost:8080/webrtc

# Or via ffprobe:
ffprobe http://localhost:8080/video.mp4
```

---
*Tested on: RPi 3B+, Bullseye, camera-streamer via crowsnest*