refactor: manage instance ID in the KV table (#1579)

backend/resources/migrations/sqlite/20260708130000_move_instance_id_to_kv.down.sql

@@ -0,0 +1,14 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+-- Move the instance ID back into the standalone app config table
+INSERT INTO app_config_variables ("key", "value")
+SELECT 'instanceId', "value"
+    FROM kv
+    WHERE "key" = 'instance_id' AND "value" IS NOT NULL
+    ON CONFLICT ("key") DO NOTHING;
+
+DELETE FROM kv WHERE "key" = 'instance_id';
+
+COMMIT;
+PRAGMA foreign_keys=ON;

backend/resources/migrations/sqlite/20260708130000_move_instance_id_to_kv.up.sql

@@ -0,0 +1,14 @@
+PRAGMA foreign_keys=OFF;
+BEGIN;
+
+-- Move the instance ID out of the standalone app config table and into the "kv" table
+INSERT INTO kv ("key", "value")
+SELECT 'instance_id', "value"
+    FROM app_config_variables
+    WHERE "key" = 'instanceId'
+    ON CONFLICT ("key") DO NOTHING;
+
+DELETE FROM app_config_variables WHERE "key" = 'instanceId';
+
+COMMIT;
+PRAGMA foreign_keys=ON;