fix(#312): deep linking for widgets, custom URLs, and Universal Links

[cassio-rossi]

Fixes deep linking end-to-end for MacMagazine post URLs. Covers three entry points under #312: widget taps, custom URLs, and Universal Links (web links opening the app instead of Safari).

Problem

1. Tapping any widget opened the app but nothing happened, on every widget size.
2. Tapping a macmagazine.com.br post link in Safari/Messages/Mail opened the browser, never the app.

Root cause

The app runs on the UIKit scene lifecycle (AppDelegate installs a SceneDelegate that hosts SceneView in a UIHostingController; the @main WindowGroup is EmptyView()). Under a UISceneDelegate, SwiftUI's .onOpenURL never fires, and SceneDelegate handled only shortcut items — so widget URLs were dropped. Separately, the app declared no Associated Domains and handled no browsing-web NSUserActivity, so it could not claim its own web URLs.

Fix

• Widget / custom URL: SceneDelegate now handles scene(_:openURLContexts:) (warm) and connectionOptions.urlContexts (cold).
• Universal Links: SceneDelegate handles scene(_:continue:) (warm) and connectionOptions.userActivities (cold), filtering for NSUserActivityTypeBrowsingWeb.
• All sources funnel into MainViewModel.openDeepLink(_:source:), which sets deepLinkPostURL and tracks analytics per source (widget vs universal_link). Reuses the existing DeepLinkNewsDetailView → MMWebView path — no new routing.
• Added com.apple.developer.associated-domains (apex + www) to debug and release entitlements.
• Added a ready-to-host reference AASA file under Support/AssociatedDomains/ (Team ID A5VW9QUF9L), scoped to /post/* so only article URLs open the app.

Verification

• ✅ Build succeeded (iPhone 17 simulator — "iPhone 17 Pro" is not installed on this machine).
• ✅ SwiftLint --strict on all changed Swift files — 0 violations.
• ✅ AASA JSON validated.
• ⚠️ Test suite not run (UNVERIFIED): changed types live in the main app target, which has no test coverage; no new test target created (per decision to ship with manual verification).
• 📱 Manual check needed: tap each widget size (cold + warm launch); once the AASA is live, tap a /post/* link and confirm it opens the article in-app.

Required outside this repo (server / portal)

1. Host Support/AssociatedDomains/apple-app-site-association at https://macmagazine.com.br/.well-known/apple-app-site-association (and www) — HTTPS, application/json, no redirect, no extension. See the README in that folder.
2. Enable Associated Domains on the com.brit.macmagazine App ID and regenerate provisioning profiles (device/TestFlight signing; simulator doesn't enforce it).

Notes / deviations

• No develop branch exists — branch is based on release/v5; PR targets release/v5.
• Left as-is by request: on medium/large widgets, WidgetView stamps a container-wide .widgetURL(content.first?.url) under .accessibilityElement(children: .combine), which limits VoiceOver users to only the first post.

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