refactor(network): consolidate network change monitoring

Remove separate watchLinkState function and integrate link state change
handling directly into monitorNetworkChanges. This consolidates network
monitoring logic into a single place and simplifies the codebase.

Update netlink dependency from v1.2.1-beta.2 to v1.3.1 and netns from
v0.0.4 to v0.0.5 to use stable versions.

cmd/cli/dns_proxy.go

@@ -1280,6 +1280,11 @@ func (p *prog) monitorNetworkChanges() error {
 			return
 		}
 
+		mainLog.Load().Debug().Msg("Link state changed, re-bootstrapping")
+		for _, uc := range p.cfg.Upstream {
+			uc.ReBootstrap()
+		}
+
 		// Get IPs from default route interface in new state
 		selfIP := defaultRouteIP()