Add pure-ffmpeg RTSP capture and camera audio for sunrise videos

Removes dependency on MotionEye or any NVR software.  Everything is now
CLI/ffmpeg configured entirely from sky-cam.conf.

capture.sh
  Long-running systemd service (one per camera) that pulls frames from the
  camera's RTSP stream at CAPTURE_INTERVAL seconds, writing HH-MM-SS.jpg
  into BASE_DIR/<cam>/YYYY-MM-DD/.  Restarts at midnight for the new date
  directory; auto-reconnects on camera disconnect.

sunrise-audio-capture.sh
  One-shot service triggered at 03:00.  Waits until (sunrise minus
  SUNRISE_PRE_MIN minus AUDIO_PRE_BUFFER_MIN), then records the RTSP audio
  stream for the full sunrise window.  Output deleted after mixing.

daily_sunrise_video.sh
  Step 3 now mixes in sunrise-audio.m4a when AUDIO_ENABLED=true and the
  file exists.  Audio is centred on actual sunrise time at natural speed
  while the video plays as the sped-up timelapse.  Uses filter_complex
  when audio is present (can't combine -vf with -filter_complex).

install.sh
  Generates sky-cam-capture-<cam>.service for each camera with CAM_RTSP_<cam>
  set, and sky-cam-audio-capture.{service,timer} when AUDIO_ENABLED=true.

sky-cam.conf
  New settings: CAM_RTSP_<cam>, CAPTURE_INTERVAL, AUDIO_ENABLED,
  AUDIO_PRE_BUFFER_MIN, CAPTURE_AUDIO_BITRATE.

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

README.md

@@ -12,11 +12,11 @@ Automated sky / timelapse camera scripts that produce:
 
 | Dependency | Notes |
 |---|---|
-| `ffmpeg` + `ffprobe` | Encoding and duration probing |
+| `ffmpeg` + `ffprobe` | Encoding, capture, audio recording, duration probing |
 | `python3` | `ephem` package for sunrise calculation, `requests` for Mattermost upload |
 | `bc` | Shell arithmetic (floating-point speed factors) |
 | `fontconfig` (`fc-match`) | Font detection for overlays — optional, falls back to hardcoded paths |
-| Camera software | e.g. `motion` — writes JPEG images named `HH-MM-SS.jpg` into `BASE_DIR/<cam>/<YYYY-MM-DD>/` |
+| IP camera with RTSP stream | `capture.sh` pulls frames directly — no NVR software needed |
 | Vivaldi Four Seasons audio | 12 MP3 files named so that `*Spring*Mvt*1*`, `*Summer*Mvt*2*`, etc. match with `find -iname` |
 
 Install Python dependencies:
@@ -60,6 +60,8 @@ Minimum settings to fill in (everything else has sensible defaults):
 | `CAMERAS` | Space-separated list of camera names, e.g. `(sunrise north)` |
 | `SUNRISE_CAM` | Which camera faces east and gets the sunrise job |
 | `LATITUDE` / `LONGITUDE` / `TIMEZONE` | Your location for sunrise calculation |
+| `CAM_RTSP_<cam>` | RTSP stream URL for each camera, e.g. `rtsp://admin:pass@192.168.1.100:554/stream1` |
+| `CAPTURE_INTERVAL` | Seconds between captured frames (default: 10) |
 | `mattermost_url` / `access_token` / `channel_id` | Mattermost upload credentials |
 
 ### 3. Install systemd timers
@@ -84,12 +86,24 @@ journalctl --user -u sky-cam-sunrise.service -f
 ## How it works
 
 ```
-Camera writes JPEGs
+Camera RTSP stream
+        │
+        ├─ capture.sh <cam>  (long-running systemd service, one per camera)
+        │    ffmpeg pulls one frame every CAPTURE_INTERVAL seconds
+        │    Writes: BASE_DIR/<cam>/YYYY-MM-DD/HH-MM-SS.jpg
+        │    Restarts at midnight for the new date directory; auto-reconnects
+        │
+        ├─ sunrise-audio-capture.sh  (runs at 03:00, waits for sunrise window)
+        │    ffmpeg records audio-only from RTSP during sunrise window
+        │    Writes: BASE_DIR/<cam>/YYYY-MM-DD/sunrise-audio.m4a
+        │    Deleted automatically after being mixed into the sunrise video
+        │
+Camera JPEGs + audio
         │
         ├─ daily_sunrise_video.sh  (runs at SCHEDULE_SUNRISE)
         │    Step 1: encode raw video from sunrise-window JPEGs
         │    Step 2: speed-adjust to SUNRISE_TARGET_SECS  → saved permanently
-        │    Step 3: burn sunrise time overlay             → final video
+        │    Step 3: burn sunrise time overlay + mix camera audio (if available)
         │    OnSuccess → sunrise2mm.py uploads to Mattermost
         │
         ├─ 4-seasons.sh <cam>  (runs at SCHEDULE_SEASONS_<cam>, processes yesterday)
@@ -134,6 +148,18 @@ You receive notifications for:
 
 ---
 
+## Camera audio (optional)
+
+If your camera has a microphone, sky-cam can mix a natural-speed 10-second audio clip (birds, rain, wind — whatever was actually happening at sunrise) into the daily sunrise video.
+
+1. Set `AUDIO_ENABLED=true` in `sky-cam.conf`
+2. Set `CAM_RTSP_<cam>` for the sunrise camera (needed for both image capture and audio)
+3. Re-run `./install.sh` to generate the `sky-cam-audio-capture.timer`
+
+The audio is recorded during the same window as the images, stored alongside them, and deleted automatically after being mixed into the final video. No audio library or AI required — it's the real sound from your camera.
+
+---
+
 ## Manual operations
 
 **Re-run today's sunrise** (e.g. after fixing a font issue):
@@ -157,6 +183,12 @@ You receive notifications for:
 ./year-end-join.sh 2025 sunrise
 ```
 
+**Check capture status**:
+```bash
+systemctl --user status sky-cam-capture-sunrise.service
+journalctl --user -u sky-cam-capture-sunrise.service -f
+```
+
 **Check logs**:
 ```bash
 journalctl --user -u sky-cam-sunrise.service