Update LinkPreview.swift

[mehmetbaykar]

Fix Xcode 26.0 Swift Concurrency error

What

• Refactor LinkPreview to use Swift Concurrency.

• Fetch metadata with async/await and set LPLinkView.metadata on the main actor:

  • Task { @MainActor in uiView.metadata = try await fetchMetadata() }
  • Introduce fetchMetadata() async throws -> LPLinkMetadata.

Why

• In Xcode 26.0 with stricter concurrency checks, the previous completion-handler approach attempted to set uiView.metadata (a @MainActor-isolated property) from a @Sendable/background context, triggering:
  “Main actor-isolated property 'metadata' cannot be mutated from a Sendable closure.”
• Using async/await removes the sendable-closure issue and guarantees UI updates occur on the main actor, aligning with Swift 6 concurrency rules.

Affected Areas

• LinkPreview.swift only.
• No behavioral change to the UI; thread-safety and compile-time correctness improved.
• Note: Requires async/await (iOS 15+/macOS 12+).

[nezhyborets]

Great, thanks!