fix: deduplicate owner access alerts per recipient (#896)

* fix: prevent duplicate access alerts to the same recipient

* fix: address recipient alert recovery review findings

* fix: reconcile unsent alerts and wait for startup migration

* fix: preserve legacy recipient alerts through upgrades

* fix: reconcile alert results and legacy recovery races

* fix: fence dispatch and clean cancelled alert metadata

* fix: fence alert preparation and retain in-flight recovery

* fix: atomically commit alert dispatch and retry deferred recovery

* fix: keep recovery lookups from blocking upstream file reads

src/core/model/anonymizedGists/anonymizedGists.schema.ts

@@ -3,6 +3,8 @@ import { Schema } from "mongoose";
 const AnonymizedGistSchema = new Schema({
   accessAlertGeneration: { type: String, select: false },
   accessAlertClaimedAt: { type: Date, select: false },
+  accessAlertAttemptId: { type: String, select: false },
+  accessAlertClaimRevision: { type: Number, select: false },
   gistId: {
     type: String,
     index: { unique: true },