fix(update): detect real image changes and improve webhook messages

Use image ID diff instead of grepping "Pulled" (which appears even
when images are already up to date). Add timestamp, stack count, and
updated/total ratio to all notification messages.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

_update/update.sh

@@ -18,7 +18,7 @@ notify() {
 : > "$LOG_FILE"
 log "Starting image update check"
 
-updated=(); failed=()
+updated=(); failed=(); checked=0
 
 for stack_dir in "$STACKS_DIR"/*/; do
   stack=$(basename "$stack_dir")
@@ -27,9 +27,13 @@ for stack_dir in "$STACKS_DIR"/*/; do
 
   log "Checking $stack"
   cd "$stack_dir"
-  pull_output=$(docker compose pull 2>&1 | tee -a "$LOG_FILE")
+  checked=$((checked + 1))
 
-  if echo "$pull_output" | grep -q " Pulled"; then
+  before=$(docker compose images -q 2>/dev/null | sort)
+  docker compose pull 2>&1 | tee -a "$LOG_FILE"
+  after=$(docker compose images -q 2>/dev/null | sort)
+
+  if [ "$before" != "$after" ]; then
     log "  Updates found — recreating containers"
     if docker compose up -d 2>&1 | tee -a "$LOG_FILE"; then
       updated+=("$stack")
@@ -45,12 +49,14 @@ done
 log "Pruning dangling images"
 docker image prune -f 2>&1 | tee -a "$LOG_FILE"
 
-if [ ${#updated[@]} -eq 0 ] && [ ${#failed[@]} -eq 0 ]; then
-  notify "#36a64f" "✅ **Update check complete** — all images up to date"
-elif [ ${#failed[@]} -gt 0 ]; then
-  notify "#cc0000" "❌ **Update failed**\nUpdated: ${updated[*]:-none}\nFailed: ${failed[*]}"
+date_str=$(date '+%Y-%m-%d %H:%M')
+
+if [ ${#failed[@]} -gt 0 ]; then
+  notify "#cc0000" "❌ **Update failed** — $date_str\nUpdated: ${updated[*]:-none}\nFailed: ${failed[*]}"
+elif [ ${#updated[@]} -gt 0 ]; then
+  notify "#36a64f" "✅ **Updates applied** — $date_str\nStacks updated (${#updated[@]}/$checked): ${updated[*]}"
 else
-  notify "#36a64f" "✅ **Updates applied**\nStacks: ${updated[*]}"
+  notify "#36a64f" "✅ **All up to date** — $date_str ($checked stacks checked)"
 fi
 
 log "Update check complete"