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

sunrise-audio-capture.sh

@@ -0,0 +1,80 @@
+#!/bin/bash
+# sunrise-audio-capture.sh — record the camera's RTSP audio stream during the
+# sunrise window so daily_sunrise_video.sh can mix in natural ambient sound
+# (birds, rain, wind) at real speed while the video plays as a timelapse.
+#
+# Triggered daily at 03:00 by sky-cam-audio-capture.timer.
+# Waits internally until (sunrise − SUNRISE_PRE_MIN − AUDIO_PRE_BUFFER_MIN),
+# then records for the full window.  Exits immediately if AUDIO_ENABLED≠true.
+#
+# Output: BASE_DIR/SUNRISE_CAM/YYYY-MM-DD/sunrise-audio.m4a
+# Deleted automatically by daily_sunrise_video.sh after mixing.
+
+set -euo pipefail
+
+SCRIPT_DIR="$(dirname "$(realpath "$0")")"
+source "$SCRIPT_DIR/sky-cam.conf"
+export TZ="$TIMEZONE"
+
+CAM="${1:-$SUNRISE_CAM}"
+
+if [ "${AUDIO_ENABLED:-false}" != "true" ]; then
+    echo "AUDIO_ENABLED is not true — skipping."
+    exit 0
+fi
+
+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
+
+# ── Sunrise time ──────────────────────────────────────────────────────────────
+sunrise_time=$(python3 "$SCRIPT_DIR/sunrise.py")
+if [ -z "$sunrise_time" ]; then
+    "$SCRIPT_DIR/notify.sh" "FAILED: audio capture — no sunrise time" \
+        "sunrise.py returned nothing — check internet/location config" || true
+    exit 1
+fi
+sunrise_time_local=$(TZ="$TIMEZONE" date -d "$sunrise_time" +"%H:%M:%S")
+echo "Sunrise (local): $sunrise_time_local"
+
+# ── Calculate wait and record duration ───────────────────────────────────────
+time_to_seconds() { IFS=':' read -r h m s <<< "$1"; echo $((10#$h*3600 + 10#$m*60 + 10#$s)); }
+
+sunrise_sec=$(time_to_seconds "$sunrise_time_local")
+buffer_sec=$(( ${AUDIO_PRE_BUFFER_MIN:-2} * 60 ))
+record_start_sec=$(( sunrise_sec - SUNRISE_PRE_MIN * 60 - buffer_sec ))
+record_dur_sec=$(( (SUNRISE_PRE_MIN + SUNRISE_POST_MIN) * 60 + buffer_sec ))
+
+midnight=$(date -d "today 00:00:00" +%s)
+now_day_sec=$(( $(date +%s) - midnight ))
+wait_sec=$(( record_start_sec - now_day_sec ))
+
+if [ "$wait_sec" -gt 0 ]; then
+    echo "Waiting ${wait_sec}s until audio window ($(date -d "@$(( midnight + record_start_sec ))" '+%H:%M:%S'))..."
+    sleep "$wait_sec"
+fi
+
+today=$(date +%Y-%m-%d)
+dir="$BASE_DIR/$CAM/$today"
+mkdir -p "$dir"
+output="$dir/sunrise-audio.m4a"
+
+echo "Recording ${record_dur_sec}s of audio → $output"
+
+if ! ffmpeg -loglevel warning \
+    -rtsp_transport tcp \
+    -i "$RTSP_URL" \
+    -t "$record_dur_sec" \
+    -vn \
+    -acodec aac -b:a "${CAPTURE_AUDIO_BITRATE:-96k}" \
+    -y "$output"; then
+    "$SCRIPT_DIR/notify.sh" "FAILED: audio capture $today" \
+        "ffmpeg audio recording failed — sunrise video will have no audio" || true
+    exit 1
+fi
+
+size=$(du -h "$output" | cut -f1)
+echo "Audio capture complete: $output  (${record_dur_sec}s, $size)"