feat(auth): a session ended for its wrong proofs warns its owner

The tenth wrong owner proof in a row ends a session (the third
reading); someone holding that session tried the password or its
codes. The register now keeps the moment with the account's password
(`account_password.sessionEndedForProofsAt`): the account's sign-in
ways and its next password sign-in carry it, until the owner dismisses
it (`password.dismissSessionEndedWarning`, their session alone: it
hides a warning and secures nothing) or sets a new password. A member
ending its own session tells the register
(`noteSessionEndedForProofs`); a register out of reach leaves the
owner unwarned, the session ended all the same.

Migration (module, Learn's and Todo's servers, Learn's device schema):
ALTER TABLE "account_password" ADD COLUMN "sessionEndedForProofsAt"
timestamp without time zone; nullable, so every row keeps its values
and has no warning.

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

packages/halkyon_base_server/migrations/20261021100319502-session-ended-warning/migration.json

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

packages/halkyon_base_server/migrations/20261021100319502-session-ended-warning/migration.sql

@@ -0,0 +1,41 @@
+BEGIN;
+
+--
+-- ACTION ALTER TABLE
+--
+ALTER TABLE "account_password" ADD COLUMN "sessionEndedForProofsAt" timestamp without time zone;
+
+--
+-- MIGRATION VERSION FOR halkyon_base
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('halkyon_base', '20261021100319502-session-ended-warning', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20261021100319502-session-ended-warning', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod', '20260824182259319', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260824182259319', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod_auth_idp
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod_auth_idp', '20260924105404509', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260924105404509', "timestamp" = now();
+
+--
+-- MIGRATION VERSION FOR serverpod_auth_core
+--
+INSERT INTO "serverpod_migrations" ("module", "version", "timestamp")
+    VALUES ('serverpod_auth_core', '20260924105232991', now())
+    ON CONFLICT ("module")
+    DO UPDATE SET "version" = '20260924105232991', "timestamp" = now();
+
+
+COMMIT;

packages/halkyon_base_server/migrations/migration_registry.txt

@@ -13,3 +13,4 @@
 20261020194005842-second-factor-waits
 20261020204618337-session-code-tries
 20261020211224310-email-code-purpose
+20261021100319502-session-ended-warning