Add random option

[dontcrash]

Updates #4756

PR required for dnsproxy
AdguardTeam/dnsproxy#467

[windsurf-bot]

Looks good to me 🤙

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[ainar-g]

This won't build without go.mod modifications. You can set the dnsproxy version to the one from your branch, temporarily, via go get.

[ainar-g]

Please update both CHANGELOG.md (that one uses KeepAChangelog standard) and openapi/CHANGELOG.md adding this change.

[ainar-g]

From what I understand, more changes to the frontend are required?

[Sil3ntVip3r]

I ported the companion feature onto current AdGuard Home master (369d47616342c8be82262bf798f2fed2f64b697f) and validated it against the patched current dnsproxy tree. No commit or push was made.

The current-master port covers the whole setting path rather than only the backend constant:

• backend configuration, current HTTP API validation/round-trip, proxy mapping, and fixtures;
• next API schema and round-trip;
• OpenAPI schema plus regenerated client_v2 model;
• both the legacy and client_v2 DNS-settings UIs, English strings, summaries, and options;
• main, next-API, and OpenAPI changelogs plus AGHTechDoc.md;
• backend, frontend-helper, and generated-API regression coverage.

The dnsproxy side uses equal weights with the existing without-replacement sampler, so random mode is uniform, failed upstreams are retried in random order, and fallback/statistics behavior is preserved. Load balancing remains RTT-weighted.

Validation passed focused backend race tests, the full backend race suite, go vet, make go-check, build, Markdown/text lint, cross-platform Go checks, generated API verification, both frontend lint/typecheck suites, 35/35 legacy tests, 621/621 client_v2 tests, both production builds, translation-key audit, and clean formatting/diff checks. I also independently reran the focused backend tests three times under -race and the new client_v2 helper test.

The remaining dependency gate is mechanical: AdGuard Home currently pins dnsproxy v0.83.1. Once the dnsproxy change from AdguardTeam/dnsproxy#467 has an accepted commit or release, update go.mod and go.sum to that revision and rerun the same gates. The temporary local workspace override used for validation was removed, so this prototype does not conceal a dependency-file change. This addresses the existing requests for frontend coverage and the main/OpenAPI changelogs.