Add Swift app for iPod contacts and calendar export

Replaces the bash/AppleScript/Python app bundle with a SwiftUI app backed
by a testable library target.

The app now reads Contacts and EventKit directly rather than sanitizing
files someone exported by hand, so the properties that break click-wheel
firmware are never written instead of being stripped afterwards: no PHOTO,
no X-, no VALARM, no VTIMEZONE, no TZID. Recurring events arrive from
EventKit already expanded into occurrences, so no RRULE is emitted either
- the open question from the previous version no longer applies.

Sanitizing existing .vcf/.ics files is kept as a second path, and gains
handling the Python lacked: vCard 2.1 quoted-printable soft line breaks,
Apple's item1. property groups, nested STANDARD/DAYLIGHT components inside
VTIMEZONE, and UTC times converted to local floating times.

Output is laid out as Contacts/ and Calendars/ subfolders mirroring the
device, one file per contact and one per calendar.

Built via SwiftPM plus Scripts/bundle.sh, which assembles and ad-hoc signs
the bundle. Ad-hoc signing is required rather than cosmetic: Contacts and
Calendars key permissions off the code signature.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01C5X1tYo9oxAfvoiFMh1QQr

Sources/IPodSyncKit/TextFile.swift

@@ -0,0 +1,51 @@
+import Foundation
+
+/// Reads text files of unknown provenance.
+///
+/// `.vcf` and `.ics` files reaching the app may have come from any address book
+/// or calendar going back twenty years, so the declared encoding — if there is
+/// one — cannot be trusted. Candidates are tried in order of likelihood.
+public enum TextFile {
+    public static func read(contentsOf url: URL) throws -> String {
+        let data = try Data(contentsOf: url)
+        return decode(data)
+    }
+
+    static func decode(_ data: Data) -> String {
+        // A UTF-8 BOM would otherwise survive into the first property name.
+        var bytes = data
+        if bytes.starts(with: [0xEF, 0xBB, 0xBF]) {
+            bytes = bytes.dropFirst(3)
+        }
+
+        for encoding in [String.Encoding.utf8, .windowsCP1252, .isoLatin1] {
+            if let text = String(data: bytes, encoding: encoding) {
+                return text
+            }
+        }
+        return String(decoding: bytes, as: UTF8.self)
+    }
+}
+
+/// One output file produced by sanitizing.
+public struct SanitizedFile: Sendable, Equatable {
+    /// Base name without extension; the caller allocates the final filename.
+    public var suggestedName: String
+    public var contents: String
+
+    public init(suggestedName: String, contents: String) {
+        self.suggestedName = suggestedName
+        self.contents = contents
+    }
+}
+
+/// The outcome of sanitizing one input file.
+public struct FileSanitizationResult: Sendable, Equatable {
+    public var files: [SanitizedFile]
+    public var warnings: [String]
+
+    public init(files: [SanitizedFile], warnings: [String] = []) {
+        self.files = files
+        self.warnings = warnings
+    }
+}