Add admin login and password change endpoints

Introduces POST /login and PATCH /password routes for admin authentication and password management. Adds corresponding schema validation for login and password change, enforces stricter password requirements, and updates adminService with JWT-based profile retrieval and improved token handling.

schemas/admin/login.js

@@ -0,0 +1,17 @@
+const z = require("zod")
+
+module.exports = {
+    POST: {
+        headers: {
+            "content-type": z.string().regex(/application\/json/i)
+        },
+        body: {
+            username: z.string()
+                .min(1),
+            password: z.string()
+                .min(8, { message: "The password must be at least 8 characters long." })
+                .regex(/[A-Z]/, { message: "The password must contain a capital letter." })
+                .regex(/[0-9]/, { message: "The password must contain a number." })
+        }
+    }
+}