Internet connectivity loss when Secure DNS (DoQ) is enabled in OpenWrt DS-Lite setup

**Issue:**
Internet connectivity is lost when Secure DNS is enabled with DNS-over-QUIC (DoQ) in a DS-Lite environment using IPv6 or dual-stack mode (NextDNS / AdGuard).

**Scenario:**
* DS-Lite WAN (IPv6-only underlay)
* Secure DNS enabled
* DoQ enabled
* ipv6_disabled=0
* dnsproxy listening only on IPv6 loopback (::1)
* Upstream DNS configured over QUIC

**Configuration:**

> /etc/config/dnsproxy

> option ipv6_disabled '0'
list listen_addr '::1'
option enabled '1'

> config dnsproxy 'tls'

option enabled '1'
option quic_port '853'

> config dnsproxy 'servers'

list bootstrap '2a07:a8c0::'
list bootstrap '2a07:a8c1::'
list upstream 'quic://dns.nextdns.io'

**Observed Behavior:**
* Internet access is lost after enabling Secure DNS with DoQ.
* DNS resolution fails, resulting in no connectivity for LAN clients.

**Impact**:
* Complete internet outage for LAN clients when Secure DNS + DoQ is enabled.

**Notes:**
* Issue occurs only with DoQ in DS-Lite.
* IPv6 connectivity is present, but DNS resolution fails.