Archive dead/manual scripts to pipeline/lib/manual (R8)

Move six scripts that are not wired into the app, scheduler, or web UI out of
the active pipeline/lib into pipeline/lib/manual, so the scheduled scripts are
easy to see and these stay available for hands-on use: convert-m4a.sh,
fix-empty-album.sh, backfill-spotify-tags.sh, backfill-buy-url.py,
recover-azuracast-playlists.py, import-dj-collection.py. Adds a README
explaining each, and extends the Dockerfile chmod to cover the new folder.
Nothing referenced these from active code (verified), so no wiring changes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pipeline/lib/manual/convert-m4a.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+# Convert m4a files in-place: AAC -> MP3 (V0 VBR), ALAC -> FLAC (lossless).
+# Preserves metadata + embedded cover art. Deletes original on success.
+set -u
+
+LOG=${ALEMBIC_CONFIG_DIR:-/config}/logs/convert-m4a-$(date +%Y%m%d-%H%M%S).log
+mkdir -p "$(dirname "$LOG")"
+
+log() { echo "[$(date -Iseconds)] $*" | tee -a "$LOG"; }
+
+OK_AAC=0
+OK_ALAC=0
+FAIL=0
+
+while IFS= read -r -d '' f; do
+  codec=$(ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of csv=p=0 "$f" 2>/dev/null | tr -d ',')
+  base="${f%.m4a}"
+  case "$codec" in
+    aac)
+      out="${base}.mp3"
+      if [[ -e "$out" ]]; then log "SKIP-EXISTS: $out"; FAIL=$((FAIL+1)); continue; fi
+      if ffmpeg -nostdin -hide_banner -loglevel error -i "$f" \
+           -map 0 -c:v copy -c:a libmp3lame -q:a 0 -id3v2_version 3 \
+           "$out" 2>>"$LOG"; then
+        rm -f "$f"
+        log "AAC→MP3:    $out"
+        OK_AAC=$((OK_AAC+1))
+      else
+        log "FAIL-AAC:   $f"
+        rm -f "$out" 2>/dev/null
+        FAIL=$((FAIL+1))
+      fi
+      ;;
+    alac)
+      out="${base}.flac"
+      if [[ -e "$out" ]]; then log "SKIP-EXISTS: $out"; FAIL=$((FAIL+1)); continue; fi
+      if ffmpeg -nostdin -hide_banner -loglevel error -i "$f" \
+           -map 0 -c:v copy -c:a flac -compression_level 8 \
+           "$out" 2>>"$LOG"; then
+        rm -f "$f"
+        log "ALAC→FLAC:  $out"
+        OK_ALAC=$((OK_ALAC+1))
+      else
+        log "FAIL-ALAC:  $f"
+        rm -f "$out" 2>/dev/null
+        FAIL=$((FAIL+1))
+      fi
+      ;;
+    *)
+      log "SKIP-OTHER ($codec): $f"
+      ;;
+  esac
+done < <(find ${MUSIC_DATA_DIR:-/data/music}/Library -type f -iname "*.m4a" -print0 2>/dev/null)
+
+log ""
+log "=== AAC→MP3:  $OK_AAC | ALAC→FLAC: $OK_ALAC | Failed: $FAIL ==="
+log "Log: $LOG"