fix(alerts): подтвердить риск ручного повтора сообщения

lib/alerts-outbox-checkpoint.ts

@@ -0,0 +1,6 @@
+// Persists ambiguous manual queue retry per source; never stores payload or credentials.
+const pending=new Set<string>(),listeners=new Set<()=>void>()
+const key=(source:string)=>"mm:alerts-outbox-pending:"+source
+export function outboxPending(source:string){try{return pending.has(source)||sessionStorage.getItem(key(source))==="true"}catch{return pending.has(source)}}
+export function subscribeOutboxPending(listener:()=>void){listeners.add(listener);return()=>{listeners.delete(listener)}}
+export function setOutboxPending(source:string,value:boolean){if(value)pending.add(source);else pending.delete(source);try{if(value)sessionStorage.setItem(key(source),"true");else sessionStorage.removeItem(key(source))}catch{/* Memory guard survives section navigation. */}for(const listener of listeners)listener()}