Add BanditURLOverrides to ConfigResponse

[myleshorton]

Summary

• Adds BanditURLOverrides map[string]string field to ConfigResponse in types.go
• Carries per-proxy callback URLs from the server-side bandit assignment system to sing-box clients
• Part of the per-ISP Thompson sampling proxy assignment feature (see getlantern/lantern-cloud and getlantern/radiance companion PRs)

Test plan

• Verify existing config serialization/deserialization is unaffected (field is omitempty)
• Confirm lantern-cloud and radiance build against this branch

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds API fields to the common package’s config request/response types to support per-proxy bandit (Thompson sampling) URL-test callback overrides and additional client version reporting.

Changes:

• Add BanditURLOverrides map[string]string to ConfigResponse (JSON bandit_url_overrides, omitempty).
• Add Version string to ConfigRequest (JSON version, omitempty).

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[Copilot]

ConfigRequest already has SingboxVersion, so introducing a second, generic Version field is ambiguous for API consumers (is it app version, API schema version, backend version, etc.?). Consider renaming to a more specific name (e.g., AppVersion/ClientVersion/APIVersion) and/or adding a brief comment clarifying its intent so it’s unambiguous when serialized as "version".

Suggested change

	Version string `json:"version,omitempty"`
	// AppVersion is the version of the Lantern client application making this request.
	AppVersion string `json:"app_version,omitempty"`

[Copilot]

There are serialization tests for ConfigResponse/ConfigRequest (see types_test.go), but they don’t exercise the newly added fields. Please extend the existing tests to cover JSON round-tripping for BanditURLOverrides and ConfigRequest.Version, and verify omitempty behavior (field absent when empty/nil).

[Copilot]

The PR description only mentions adding BanditURLOverrides to ConfigResponse, but this diff also adds Version to ConfigRequest. If Version is intentional, please update the PR description (and any companion PR references) to reflect this additional API surface change; otherwise, consider dropping it from this PR to keep scope aligned.