fix(common): retry Tailscale IP resolution up to 3 times before failing

The first cron run of critical_sync_maintenance failed because Tailscale
had a transient moment at startup. resolve_remote_ip() now retries 3 times
with a 5s delay before giving up, making it resilient to brief daemon
hiccups without masking real peer-offline conditions.

common.sh

@@ -613,7 +613,9 @@ detect_hosts() {
 resolve_remote_ip() {
     log "Resolving remote IP for $REMOTE_SERVER_NAME..."
     local ts_name="${REMOTE_SERVER_NAME,,}"
+    local attempts=3
 
+    for ((i=1; i<=attempts; i++)); do
         # Direct lookup — works when MagicDNS short-name resolution is active
         REMOTE_SERVER=$(tailscale ip -4 "$ts_name" 2>/dev/null)
 
@@ -622,8 +624,12 @@ resolve_remote_ip() {
             REMOTE_SERVER=$(tailscale status 2>/dev/null | awk -v name="$ts_name" '$2 ~ "^" name { print $1; exit }')
         fi
 
+        [[ -n "$REMOTE_SERVER" ]] && break
+        [[ $i -lt $attempts ]] && { warn "Tailscale resolution attempt $i/$attempts failed — retrying in 5s..."; sleep 5; }
+    done
+
     if [[ -z "$REMOTE_SERVER" ]]; then
-        error "Failed to resolve Tailscale IP for $REMOTE_SERVER_NAME"
+        error "Failed to resolve Tailscale IP for $REMOTE_SERVER_NAME after $attempts attempts"
         error "Check: tailscale status | grep $ts_name"
         exit 1
     fi