feat(ui): optional gender radio in the people form and 个人资料 (T2)

One ProfileGenderField (女 / 男 / 不填, 44px, one hint line) in the
people-archive edit form (saved with the form, 不填 → null) and in
设置 → 个人资料 for the owner (saves on its own PATCH; birth-data saves never
send gender). The detail card shows 性别 (未填 when empty). Not asked in
onboarding. DESIGN/VOICE updated; 390/1280 screenshots with fictional data.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017eEAG8HD3mm8gsKXgk8uU8

frontend/src/hooks/use-profile-onboarding.ts

@@ -36,6 +36,7 @@ import {
   selectedBirthPlace,
 } from "@/lib/home-profile";
 import { resolveAyanamsa } from "@/lib/ayanamsa";
+import { withSavedGender, type ProfileGender } from "@/lib/profile-gender";
 import { createStartGreeting } from "@/lib/starter-greeting";
 import { clearHomeWarmSnapshot } from "@/lib/home-warm-snapshot";
 import {
@@ -200,6 +201,26 @@ export function useProfileOnboarding(params: ProfileOnboardingParams) {
     }
   }
 
+  /**
+   * The owner's optional gender (设置 → 个人资料). A PATCH of this one field:
+   * birth-data saves never send it, so they can never clear it.
+   */
+  async function persistGender(gender: ProfileGender | null): Promise<void> {
+    if (!account) throw new Error("账户尚未加载完成");
+    const response = await fetch("/api/account", {
+      method: "PATCH",
+      credentials: "same-origin",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ gender }),
+    });
+    const payload = await response.json().catch(() => null) as { error?: string } | null;
+    if (!response.ok) throw new Error(payload?.error || "性别没保存上，再试一次。");
+    const apply = (current: Profile): Profile => ({ ...current, gender });
+    setProfile(apply);
+    setProfileDraft(apply);
+    setAccount((current) => current ? { ...current, profile: withSavedGender(current.profile, gender) } : current);
+  }
+
   async function persistProfile(nextProfile: Profile): Promise<Profile> {
     if (!account) throw new Error("账户尚未加载完成");
     if (process.env.NODE_ENV === "development" && uiPreview.current) return nextProfile;
@@ -427,6 +448,7 @@ export function useProfileOnboarding(params: ProfileOnboardingParams) {
     openAccountDialog,
     closeAccountDialog,
     persistAvatar,
+    persistGender,
     persistProfile,
     assessSavedBirthTime,
     saveProfile,