fix: stop persisting generated signup passwords in session account records

- 合并 PR #100 的核心改动：移除步骤 3 向 state.accounts 写入明文 password 的逻辑
- 本地补充修复：无额外代码修复，仅将目标分支从 master 校正到 dev 并完成审查状态回写
- 影响范围：background/steps/fill-password.js 的账号记录持久化流程

background/steps/fill-password.js

@@ -30,7 +30,7 @@
       await setPasswordState(password);
 
       const accounts = state.accounts || [];
-      accounts.push({ email: resolvedEmail, password, createdAt: new Date().toISOString() });
+      accounts.push({ email: resolvedEmail, createdAt: new Date().toISOString() });
       await setState({ accounts });
 
       await chrome.tabs.update(signupTabId, { active: true });