后端：资料距离、语音图片会员限制、免短信注册、AI 托管回复修复

- 单用户资料接口补上距离：此前只有推荐/附近列表会算距离，资料页和
  聊天头部因此无内容可显示。沿用同一套 haversine 与隐私开关。
- 语音/图片消息可限定会员发送，两个开关在管理端「运营配置」中修改
  （迁移 032）。校验放在 persistMessageContext，HTTP 与 WebSocket
  两条发送路径都覆盖；文本消息永不受限。
- 短信服务关闭时注册不再要求验证码：关掉之后没人能拿到验证码，继续
  要求就等于关闭注册通道。重置密码不做同样放宽，那里缺验证码等于
  凭手机号夺号。app/config 增加 smsVerification 供客户端决定表单形态。
- 修复 AI 托管账号之间不回复：原规则按「发送方是否托管账号」拦截，
  把真人操作测试号的正常对话也挡了。改为标记 worker 自己写入的回复，
  只对 AI 生成的消息跳过入队。
- ai.default_model_id 同时接受模型 ID 与名称，填名称时不再被 MySQL
  静默转成 0 而使配置失效。
- 聊天媒体留存管理与清理任务（迁移 033，两台线上均已应用）。

新增集成测试均针对真实 MySQL：会员限制、免短信注册、AI 入队规则、
默认模型解析、资料距离。

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

im/backend/internal/app/membership_limits.go

@@ -120,3 +120,44 @@ func (a *App) reserveDailyActiveChat(ctx context.Context, tx *sql.Tx, conversati
 	_, err = tx.ExecContext(ctx, `UPDATE im_daily_active_chat_usage SET used_count=used_count+1 WHERE user_id=? AND usage_date=CURRENT_DATE()`, senderID)
 	return err
 }
+
+const (
+	messageTypeImage = 2
+	messageTypeVoice = 3
+)
+
+// messageMembershipGateError names the message kind the reader was blocked on,
+// so the client can offer the right upgrade prompt instead of a generic error.
+type messageMembershipGateError struct{ Kind string }
+
+func (e *messageMembershipGateError) Error() string {
+	return fmt.Sprintf("发送%s消息需要开通会员", e.Kind)
+}
+
+// hasActiveMembership uses the same subscription row that /membership/status
+// reports as "active", so the app never offers what the server will refuse.
+// Every grant path — order, admin, gateway callback — writes that row.
+func (a *App) hasActiveMembership(ctx context.Context, userID int64) bool {
+	var one int
+	return a.db.QueryRowContext(ctx, `SELECT 1 FROM subscriptions WHERE user_id=? AND status=1 AND started_at<=NOW(3) AND expires_at>NOW(3) LIMIT 1`, userID).Scan(&one) == nil
+}
+
+// messageMembershipGate reports whether one message type is members-only and
+// what to call it. Both switches are edited from the admin console.
+func (a *App) messageMembershipGate(ctx context.Context, messageType int) (string, bool) {
+	switch messageType {
+	case messageTypeImage:
+		return "图片", a.configBool(ctx, "membership.image_message_requires_vip", false)
+	case messageTypeVoice:
+		return "语音", a.configBool(ctx, "membership.voice_message_requires_vip", false)
+	}
+	return "", false
+}
+
+func (a *App) ensureMessageMembership(ctx context.Context, senderID int64, messageType int) error {
+	kind, gated := a.messageMembershipGate(ctx, messageType)
+	if !gated || a.hasActiveMembership(ctx, senderID) {
+		return nil
+	}
+	return &messageMembershipGateError{Kind: kind}
+}