feat(auth): add role guards and protect admin routes

src/schemas/auth.schema.ts

@@ -0,0 +1,18 @@
+import { z } from "zod"
+
+export const signInSchema = z.object({
+  username: z
+    .string()
+    .min(1, {
+      error: "Invalid username",
+    })
+    .nonempty("Username is required"),
+  password: z
+    .string()
+    .min(3, {
+      error: "Password is too short",
+    })
+    .nonempty("Password is required"),
+})
+
+export type SignInFormType = z.infer<typeof signInSchema>