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

capture.sh

@@ -0,0 +1,62 @@
+#!/bin/bash
+# capture.sh <cam-name> — continuous JPEG frame capture from a camera's RTSP
+# stream.  Replaces MotionEye or any NVR for sky-cam's timelapse pipeline.
+# Pure ffmpeg — no NVR software required.
+#
+# Run as a long-running systemd service (Type=simple), one per camera.
+# install.sh generates sky-cam-capture-<cam>.service automatically when
+# CAM_RTSP_<cam> is set in sky-cam.conf.
+#
+# Writes: BASE_DIR/<cam>/YYYY-MM-DD/HH-MM-SS.jpg
+# Restarts ffmpeg at midnight so images land in the correct date directory.
+# On camera disconnect, waits 30 s then reconnects automatically.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(dirname "$(realpath "$0")")"
+source "$SCRIPT_DIR/sky-cam.conf"
+export TZ="$TIMEZONE"
+
+CAM="${1:-$CAM_NAME}"
+
+rtsp_var="CAM_RTSP_${CAM}"
+RTSP_URL="${!rtsp_var:-}"
+if [ -z "$RTSP_URL" ]; then
+    echo "ERROR: CAM_RTSP_${CAM} not set in sky-cam.conf"
+    exit 1
+fi
+
+INTERVAL="${CAPTURE_INTERVAL:-10}"
+echo "Starting capture: cam=$CAM  interval=${INTERVAL}s"
+
+while true; do
+    today=$(date +%Y-%m-%d)
+    dir="$BASE_DIR/$CAM/$today"
+    mkdir -p "$dir"
+
+    # Run until midnight + 5 s so the new day's directory is ready on restart
+    midnight=$(date -d "tomorrow 00:00:00" +%s)
+    now=$(date +%s)
+    duration=$(( midnight - now + 5 ))
+
+    echo "[$(date '+%Y-%m-%d %H:%M:%S')] Capturing → $dir  (rollover in ${duration}s)"
+
+    # -strftime 1 expands %H-%M-%S in the output path using the frame timestamp
+    ffmpeg -loglevel warning \
+        -rtsp_transport tcp \
+        -i "$RTSP_URL" \
+        -t "$duration" \
+        -vf "fps=1/${INTERVAL}" \
+        -f image2 \
+        -strftime 1 \
+        -q:v 2 \
+        "${dir}/%H-%M-%S.jpg" || true
+
+    # If ffmpeg exited before midnight the camera dropped — wait then retry
+    if [ "$(date +%s)" -lt "$midnight" ]; then
+        echo "[$(date '+%Y-%m-%d %H:%M:%S')] [$CAM] stream lost — retrying in 30s"
+        sleep 30
+    else
+        sleep 2  # brief pause at midnight before day rollover restart
+    fi
+done