[client] Fix dns forwarder handling of requested record types

[lixmal]

Describe your changes

The forwarder always responded with whatever A or AAAA records it got, regardless of the query type.

Issue ticket number and link

Checklist

• Is it a bug fix
• Is a typo/documentation fix
• Is a feature enhancement
• It is a refactor
• Created tests that fail without the change (if possible)
• Extended the README / documentation, if necessary

[Copilot]

Pull Request Overview

This pull request fixes the DNS forwarder so that it only responds with the record types requested (A or AAAA) instead of returning any record type.

• Introduces a switch-case in the DNS query handler to select the appropriate network for A or AAAA queries and returns a “not implemented” response for other types.
• Updates the resolver lookup to use net.DefaultResolver.LookupNetIP with the new netip type conversions and refactors the addition of IP addresses into a helper function.
• Updates the upstream timeout constant usage across DNS upstream endpoints and tests.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
client/internal/dnsfwd/forwarder.go	Implements type-specific handling for A/AAAA queries and refactors IP record addition.
client/internal/dns/upstream_test.go	Updates timeout constant usage in tests.
client/internal/dns/upstream_ios.go	Updates timeout constant usage for iOS-specific DNS upstream.
client/internal/dns/upstream_android.go	Updates timeout constant usage for Android-specific DNS upstream.
client/internal/dns/upstream.go	Introduces UpstreamTimeout constant and updates timeout usages.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud