feat(ui): update channel preference (Stable/Beta) missing from General Settings

[bocan]

Update channel preference (Stable/Beta) missing from General Settings

Problem

There is no user-facing toggle or picker to choose between the stable and beta Sparkle update channels. Phase 16 spec §12 requires a Stable/Beta channel preference. Currently there is no updates.betaChannel UserDefaults key, no UI to set it, and UpdateController.feedURLString(for:) (once Sparkle is added — see #205) won't know which channel to return.

Required changes

1. Register default

In BocanApp.registerDefaults():

"updates.betaChannel": false,

2. Add to General Settings

In Modules/UI/Sources/UI/Settings/GeneralSettingsView.swift, add a new section:

Section("Software Updates") {
    Toggle(isOn: Binding(
        get: { UserDefaults.standard.bool(forKey: "updates.betaChannel") },
        set: { UserDefaults.standard.set($0, forKey: "updates.betaChannel") }
    )) {
        VStack(alignment: .leading, spacing: 2) {
            Text("Receive beta updates")
            Text("Opt in to early-access releases. Betas may have bugs.")
                .font(.caption)
                .foregroundStyle(.secondary)
        }
    }
    .help("When enabled, Bòcan will offer beta (pre-release) versions in addition to stable releases.")
}

3. Wire in UpdateController

UpdateController.feedURLString(for:) (see #205) already reads UserDefaults.standard.bool(forKey: "updates.betaChannel"). No additional wiring needed once Sparkle is integrated.

4. Localization

Add the new strings to Modules/UI/Sources/UI/Resources/Localizable.xcstrings:

• "Software Updates" (settings section header)
• "Receive beta updates" (toggle label)
• "Opt in to early-access releases. Betas may have bugs." (caption)

Acceptance criteria

• General Settings has a "Software Updates" section with "Receive beta updates" toggle
• Default is off (false)
• Toggling on causes UpdateController to return https://bocan.app/appcast-beta.xml as the feed URL
• Toggling off returns to https://bocan.app/appcast.xml
• Toggle has a .help() modifier
• All strings added to Localizable.xcstrings

Dependencies

Blocked by #205 (Sparkle not yet integrated).

[bocan]

Gonna hold off on this one.