feat: complete remaining Go backend modules

contracts/auth/password-change-v1.json

@@ -0,0 +1,11 @@
+{
+  "version": 1,
+  "method": "POST",
+  "path": "/api/auth/password/change",
+  "request": ["currentPassword", "newPassword", "confirmPassword"],
+  "minimumPasswordLength": 8,
+  "successStatus": 200,
+  "replacementCookie": "zhinian_session",
+  "incrementsSessionVersion": true,
+  "publicUserExcludes": ["passwordHash", "passwordSalt", "sessionVersion", "accessToken", "tokenType"]
+}