feat(varaverk): append logs per run with timestamp separator

run_job.sh was overwriting the log on every cron fire, making it
impossible to see run history. Switch to append mode, print a
── YYYY-MM-DD HH:MM:SS ── separator before each run, and trim to
the last 1000 lines after each run to keep logs bounded.

Plugin/usr/local/emhttp/plugins/varaverk/run_job.sh

@@ -5,7 +5,7 @@
 # Usage: bash run_job.sh <job_id> <script_path> [flags...]
 #
 # Writes: /var/log/varaverk/<id>.json — status, timestamps, exit code, pid
-#         /var/log/varaverk/<id>.log  — latest run output (overwritten each run)
+#         /var/log/varaverk/<id>.log  — appended per run, trimmed to LOG_MAX_LINES
 #
 # Status values: running → ok (exit 0) | warn (exit 1) | error (exit 2+)
 
@@ -17,6 +17,7 @@ LOG_DIR="/var/log/varaverk"
 BASE="${JOB_ID%.sh}"
 LOG_FILE="$LOG_DIR/$BASE.log"
 STAT_FILE="$LOG_DIR/$BASE.json"
+LOG_MAX_LINES=1000
 
 mkdir -p "$(dirname "$LOG_FILE")" "$(dirname "$STAT_FILE")"
 
@@ -24,7 +25,10 @@ START=$(date +%s)
 printf '{"id":"%s","status":"running","start":%s,"pid":%s}\n' \
     "$JOB_ID" "$START" "$$" > "$STAT_FILE"
 
-bash "$SCRIPT" "$@" > "$LOG_FILE" 2>&1
+printf '\n── %s ────────────────────────────────────────────────\n' \
+    "$(date '+%Y-%m-%d %H:%M:%S')" >> "$LOG_FILE"
+
+bash "$SCRIPT" "$@" >> "$LOG_FILE" 2>&1
 EC=$?
 
 END=$(date +%s)
@@ -36,4 +40,10 @@ fi
 printf '{"id":"%s","status":"%s","start":%s,"end":%s,"exit":%s}\n' \
     "$JOB_ID" "$STATUS" "$START" "$END" "$EC" > "$STAT_FILE"
 
+# Trim to last LOG_MAX_LINES to prevent unbounded growth
+line_count=$(wc -l < "$LOG_FILE" 2>/dev/null || echo 0)
+if [ "$line_count" -gt "$LOG_MAX_LINES" ]; then
+    tail -n "$LOG_MAX_LINES" "$LOG_FILE" > "${LOG_FILE}.tmp" && mv "${LOG_FILE}.tmp" "$LOG_FILE"
+fi
+
 exit $EC