Add peer-share toggle to lantern-core (Share My Connection PR 3/4)

[myleshorton]

PR 3 of 4 implementing the lantern-side wiring for Share My Connection (peer-proxy). Builds on radiance #458 (peer module) and #460 (LocalBackend wiring).

Blocked on radiance #460 merging. This PR temporarily bumps radiance to the tip of fisk/peer-localbackend so the new settings.PeerShareEnabledKey is available. Re-pin to a release tag after radiance #460 merges.

Lifecycle

```
Dart toggle → setPeerProxyEnabled(C.int)
→ LanternCore.SetPeerShareEnabled(bool)
→ ipc.Client.PatchSettings({PeerShareEnabledKey: ...})
→ radiance LocalBackend.PatchSettings dispatch
→ peer.Client.Start / Stop
```

What's in here

• lantern-core/core.go — new PeerShare interface (mirrors Ads / SmartRouting), embedded in Core. SetPeerShareEnabled patches via the radiance IPC client; IsPeerShareEnabled reads the snapshot.
• lantern-core/ffi/ffi.go — //export setPeerProxyEnabled and //export isPeerProxyEnabled, mirroring setBlockAdsEnabled / isBlockAdsEnabled exactly.
• lantern-core/mobile/mobile.go — gomobile-bind surface (SetPeerShareEnabled / IsPeerShareEnabled) so Android can toggle once Dart wires it up.
• go.mod / go.sum — provisional radiance bump to 6a238ce (fisk/peer-localbackend tip).

Naming

C export name uses PeerProxy to match the existing user-facing terminology in this repo (the toggle stub in lib/features/setting/vpn_setting.dart was drafted as "Peer Proxy"). Internal Go names use PeerShare to match the radiance setting key (PeerShareEnabledKey). The Dart side will route setPeerProxyEnabled in PR 4.

What's NOT in here (PR 4)

• ffigen regen for the auto-generated Dart bindings.
• LanternFFIService.setPeerProxyEnabled Dart method.
• app_setting_notifier.setPeerProxy() body rewrite (mirror setBlockAds rollback pattern).
• Optional status indicator wired to the new SSE (/peer/status/events from radiance Write a complete spec of Lantern in preparation for a security audit #460).

Test plan

• go build ./lantern-core/...
• go test ./lantern-core/...
• golangci-lint run --new-from-rev=origin/main ./lantern-core/...
• End-to-end manual deferred until PR 4 (when the Dart toggle lands).

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds Lantern-side wiring for the Share My Connection feature by introducing a new peer-share toggle in lantern-core, exposed through both gomobile bindings and the existing C FFI surface, and backed by a radiance settings patch.

Changes:

• Add a PeerShare interface to lantern-core and implement SetPeerShareEnabled / IsPeerShareEnabled via radiance settings (PatchSettings + snapshot read).
• Expose the toggle through FFI exports (setPeerProxyEnabled / isPeerProxyEnabled) and gomobile (SetPeerShareEnabled / IsPeerShareEnabled).
• Temporarily bump github.com/getlantern/radiance to a newer pseudo-version containing settings.PeerShareEnabledKey.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lantern-core/mobile/mobile.go	Adds gomobile-facing setters/getters to toggle peer-share and query its current state.
lantern-core/ffi/ffi.go	Adds C-exported functions to toggle/query peer-share from the Dart/FFI layer.
lantern-core/core.go	Introduces PeerShare interface and core implementation backed by radiance settings.
go.mod	Updates the radiance dependency to a newer pseudo-version for the new settings key.
go.sum	Updates sums to match the radiance version bump.

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