feat: 完善后端脚手架基础能力

migrations/sqlite/20260809000100_create_users.sql

@@ -0,0 +1,6 @@
+CREATE TABLE `users` (
+  `id` integer PRIMARY KEY AUTOINCREMENT,
+  `username` text NOT NULL,
+  `password` text NOT NULL
+);
+CREATE UNIQUE INDEX `idx_users_username` ON `users` (`username`);

migrations/sqlite/atlas.sum

@@ -0,0 +1,2 @@
+h1:rMchBIYMumzVULbnGqmawAZKbkJM8S9Hjok6Qg4zagU=
+20260809000100_create_users.sql h1:JEyy3iqFHNJb4WSR8YNhbFqhxd+B3JIwqxpDWJF393o=