fix(notifications): neutralize satellite-local node names in alert bodies (#1640)

* fix(notifications): neutralize satellite-local node names in alert bodies

Fleet-aggregated alerts embedded each instance seed name (often Local)
while the hub badge already named the remote. Drop identity prefixes and
use type-aware local wording so attribution stays on the badge.

* fix(docs): correct image-update default check cadence

Operator docs still said six-hour polling; the seeded default is two
hours in interval mode, and the cadence is configurable or cron-based.

* test(notifications): assert hub stamps roster name on neutral remote bodies

Cover the fan-in path that attaches hub roster identity while leaving the
satellite message body unchanged.

backend/src/services/MonitorService.ts

@@ -765,7 +765,8 @@ export class MonitorService {
                                 const safeCurrent = typeof currentValue === 'number' ? Number(currentValue.toFixed(2)) : currentValue;
                                 const safeThreshold = typeof rule.threshold === 'number' ? Number(rule.threshold.toFixed(2)) : rule.threshold;
 
-                                const message = `[Node: ${node.name}] The **${metricName}** for **${rule.stack_name}** ${operatorPhrase} **${safeThreshold}${unit}** (Currently: ${safeCurrent}${unit}).`;
+                                // Node-neutral body: the hub bell badge attributes remotes.
+                                const message = `The **${metricName}** for **${rule.stack_name}** ${operatorPhrase} **${safeThreshold}${unit}** (Currently: ${safeCurrent}${unit}).`;
 
                                 console.log(`[MonitorService] Alert fired: rule ${ruleId} on stack "${rule.stack_name}": ${metricName} ${operatorPhrase} ${safeThreshold}${unit}`);
                                 await NotificationService.getInstance().dispatchAlert(