Add subscription usage and bulk refresh

[PhoenixNil]

Summary

• Parse and persist provider subscription-userinfo traffic and expiry metadata.
• Display available usage and expiry in subscription cards, with localized bulk-refresh progress.
• Refresh all subscriptions with bounded concurrency, serialize server saves, and retry zero-result subscriptions with a Clash-compatible user agent.

Why

Providers often expose quota and expiry only through response headers or require a Clash-compatible user agent. Updating several subscriptions one at a time also made keeping subscription data current unnecessarily tedious.

User impact

Subscription cards now show traffic usage and expiry when the provider exposes them, and the management dialog offers an Update all action with progress feedback.

Validation

• dotnet test XrayUI.Tests\XrayUI.Tests.csproj --no-restore --verbosity minimal — 65 passed
• dotnet build XrayUI-dev.csproj --no-restore --configuration Debug --verbosity minimal — succeeded with 0 warnings and 0 errors

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Show expiry when a subscription has no finite quota

For providers that report an expiry but an unlimited quota (total=0) or omit total, HasTraffic is false even though HasExpiry is true. This hides the new traffic/expiry line and instead displays the URL, so the provider's expiry metadata is never shown. Make this visibility depend on either traffic or expiry (and hide the URL under the same condition).

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