feat: enrich Settings → App Info with metadata & resource links (#56)

Replaces the three-row App Info screen with a full About/Resources/Support/
Legal layout, driven by a declarative AppInfoRow model with all URLs centralized
in one AppLinks namespace.

- About: Version now shows "5.0.0 (build N)" (CFBundleShortVersionString +
  CFBundleVersion), plus Storage, Backup Schema, and Minimum iOS (17.6).
- Resources: What's New (bundled ReleaseNotes.json sheet, no network),
  Documentation & FAQ, Source Code, Privacy Policy, and Acknowledgements
  ("no third-party dependencies" + MIT license).
- Support: Report an Issue (a sheet that shows the locally-assembled
  version/OS/device diagnostics before offering Email or GitHub — nothing is
  collected silently) and Contact (mailto).
- Support the App: Rate (SwiftUI's @Environment(\.requestReview), which handles
  the scene internally and respects Apple's throttling — the modern, safer
  equivalent of the issue's SKStoreReviewController + connectedScenes path) and
  Share (ShareLink to the App Store listing).
- Legal: copyright footer with the current year.

External rows use Link/openURL with an "opens outside the app" accessibility
hint; the screen is standard adaptive Form controls with semantic colors, so it
tracks Dynamic Type and light/dark automatically.

New files (AppLinks, AppInfo, ReleaseNotes[.swift/.json], AppInfoView) auto-
compile/bundle via the synchronized DomainDig/ group. AppInfoTests covers the
mailto builder, version format, diagnostics contents, and that the bundled notes
ship and parse. Unit suite green.

Placeholder pending the App Store listing: AppLinks.appStoreID (the review/share
URLs derive from it), flagged with a TODO.

1 files changed, 52 insertions, 0 deletions

diff --git a/DomainDig/AppInfo.swift b/DomainDig/AppInfo.swift
new file mode 100644
index 0000000..28b0826
--- /dev/null
+++ b/DomainDig/AppInfo.swift
@@ -0,0 +1,52 @@
+import Foundation
+import UIKit
+
+/// Runtime app metadata read from the bundle, plus the locally-assembled
+/// diagnostics used to prefill an issue report. Nothing here touches the network
+/// or collects any identifier beyond the app version, iOS version, and hardware
+/// model string.
+enum AppInfo {
+    /// CFBundleShortVersionString (marketing version), falling back to the
+    /// compiled-in `AppVersion.current` if the Info.plist key is missing.
+    static var marketingVersion: String {
+        Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? AppVersion.current
+    }
+
+    /// CFBundleVersion (build number).
+    static var buildNumber: String {
+        Bundle.main.infoDictionary?["CFBundleVersion"] as? String ?? "—"
+    }
+
+    /// "5.0.0 (build 45)" — version alongside build, as the App Info row shows it.
+    static var versionDisplay: String {
+        "\(marketingVersion) (build \(buildNumber))"
+    }
+
+    static let minimumOS = "17.6"
+
+    static var systemVersion: String {
+        UIDevice.current.systemVersion
+    }
+
+    /// Hardware model identifier (e.g. "iPhone15,2") — a model string, not a
+    /// per-device identifier.
+    static var deviceModel: String {
+        var systemInfo = utsname()
+        uname(&systemInfo)
+        let identifier = withUnsafeBytes(of: &systemInfo.machine) { raw -> String in
+            let bytes = raw.prefix { $0 != 0 }
+            return String(decoding: bytes, as: UTF8.self)
+        }
+        return identifier.isEmpty ? "Unknown" : identifier
+    }
+
+    /// Diagnostics prefilled into an issue report. Shown to the user before any
+    /// send — never collected silently.
+    static var diagnosticsReport: String {
+        """
+        DomainDig \(versionDisplay)
+        iOS \(systemVersion)
+        Device \(deviceModel)
+        """
+    }
+}