fix(auth): a hold-out moves a reset on only by its own time, and a reset lives 30 days at most

The reading of the full reading's fixes found that every refusal at the
address's ceiling moved a reset to 72 hours after it (A1): someone who
knows only the address kept the owner's own reset from ever taking effect
with one burst every three days, and kept a forgotten one alive (A2).

Now a hold-out that begins before a reset takes effect moves it on only by
the time it holds the owner out and no hold-out counted before did
(account_reset.heldOutUntil, under a row lock), so the owner gets 72 hours
outside hold-outs in total; and every reset not carried out lapses 30 days
after it was asked (resetLivesAtMost), whatever moved it, besides a week
after it took effect.

Migration (module, Learn's and Todo's servers, Learn's device schema):
ALTER TABLE "account_reset" ADD COLUMN "heldOutUntil" timestamp without
time zone; nullable, existing rows counted from now on.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_server/migrations/20261021134803749-reset-hold-outs/migration.json

@@ -0,0 +1,33 @@
+{
+  "__className__": "serverpod.DatabaseMigration",
+  "actions": [
+    {
+      "__className__": "serverpod.DatabaseMigrationAction",
+      "type": "alterTable",
+      "alterTable": {
+        "__className__": "serverpod.TableMigration",
+        "name": "account_reset",
+        "schema": "public",
+        "addColumns": [
+          {
+            "__className__": "serverpod.ColumnDefinition",
+            "name": "heldOutUntil",
+            "fieldName": "heldOutUntil",
+            "columnType": 4,
+            "isNullable": true,
+            "dartType": "DateTime?"
+          }
+        ],
+        "deleteColumns": [],
+        "modifyColumns": [],
+        "addIndexes": [],
+        "deleteIndexes": [],
+        "addForeignKeys": [],
+        "deleteForeignKeys": [],
+        "warnings": []
+      }
+    }
+  ],
+  "warnings": [],
+  "migrationApiVersion": 1
+}