Add employees management module with database schema and validation

- Introduced `EmployeesModule` to manage employee data, including read and write controllers.
- Created database migrations for the `employees` table, including constraints and unique indexes.
- Implemented validation for employee fields such as name, code, and position with corresponding utility functions.
- Developed service and repository layers for handling employee data operations.
- Added unit tests for the employees service, repository, and controllers to ensure functionality and correctness.
- Updated application module to include the new `EmployeesModule` for better organization.

drizzle/migrations/meta/_journal.json

@@ -50,6 +50,13 @@
       "when": 1787554000000,
       "tag": "0006_customers",
       "breakpoints": true
+    },
+    {
+      "idx": 7,
+      "version": "7",
+      "when": 1787555000000,
+      "tag": "0007_employees",
+      "breakpoints": true
     }
   ]
 }