chore: add migration for remote invalid local flag (#10174)

Follow to resp. migration for the change in this commit:

7b319111d3

---------

Co-authored-by: Jakob Borg <jakob@kastelo.net>

internal/db/sqlite/sql/migrations/folder/02-remove-invalid.sql

@@ -0,0 +1,20 @@
+-- Copyright (C) 2025 The Syncthing Authors.
+--
+-- This Source Code Form is subject to the terms of the Mozilla Public
+-- License, v. 2.0. If a copy of the MPL was not distributed with this file,
+-- You can obtain one at https://mozilla.org/MPL/2.0/.
+
+-- Remote files with the invalid bit instead gain the RemoteInvalid local
+-- flag.
+UPDATE files
+    SET local_flags = local_flags | {{.FlagLocalRemoteInvalid}}
+    FROM (
+        SELECT idx FROM devices
+        WHERE device_id = '7777777-777777N-7777777-777777N-7777777-777777N-7777777-77777Q4'
+    ) AS local_device
+    WHERE invalid AND device_idx != local_device.idx
+;
+
+-- The invalid column goes away.
+ALTER TABLE files DROP COLUMN invalid
+;