Add save file option for profile sharing

Add "Save File" and "Save Content JSON" options to profile share menu,
allowing users to save profiles directly to a chosen location using
fileExporter instead of the system share sheet.

Library/Database/Profile+Transferable.swift

@@ -109,3 +109,61 @@ public struct TypedProfile: Transferable, Codable {
 public extension UTType {
     static var profile: UTType { .init(exportedAs: "io.nekohasekai.sfavt.profile") }
 }
+
+// MARK: - FileDocument for Export
+
+public struct ProfileExportDocument: FileDocument {
+    public static var readableContentTypes: [UTType] { [.profile] }
+
+    public let data: Data
+    public let filename: String
+
+    public init(content: LibboxProfileContent) throws {
+        guard let encoded = content.encode() else {
+            throw NSError(domain: "ProfileExportDocument", code: -1, userInfo: [NSLocalizedDescriptionKey: "Failed to encode profile"])
+        }
+        data = encoded
+        filename = "\(content.name).bpf"
+    }
+
+    public init(configuration: ReadConfiguration) throws {
+        guard let data = configuration.file.regularFileContents else {
+            throw CocoaError(.fileReadCorruptFile)
+        }
+        self.data = data
+        filename = "profile.bpf"
+    }
+
+    public func fileWrapper(configuration _: WriteConfiguration) throws -> FileWrapper {
+        FileWrapper(regularFileWithContents: data)
+    }
+}
+
+public struct ProfileJSONExportDocument: FileDocument {
+    public static var readableContentTypes: [UTType] { [.json] }
+
+    public let content: String
+    public let filename: String
+
+    public init(jsonContent: String, name: String) {
+        content = jsonContent
+        filename = "\(name).json"
+    }
+
+    public init(configuration: ReadConfiguration) throws {
+        guard let data = configuration.file.regularFileContents,
+              let content = String(data: data, encoding: .utf8)
+        else {
+            throw CocoaError(.fileReadCorruptFile)
+        }
+        self.content = content
+        filename = "profile.json"
+    }
+
+    public func fileWrapper(configuration _: WriteConfiguration) throws -> FileWrapper {
+        guard let data = content.data(using: .utf8) else {
+            throw CocoaError(.fileWriteInapplicableStringEncoding)
+        }
+        return FileWrapper(regularFileWithContents: data)
+    }
+}