Add EntityImporter protocol (from t_a150f356)

iOS/MonsterCards/ImportExport/EntityImporter.swift

@@ -0,0 +1,50 @@
+//
+//  EntityImporter.swift
+//  MonsterCards
+//
+//  Imported from Android commit 044202c — refactors monster importers to a common interface.
+//
+
+import Foundation
+
+/// Protocol that all entity importers implement, matching the Java `EntityImporter<T>` interface.
+/// Each importer decides whether it can handle the input and then parses it into domain objects.
+protocol EntityImporter {
+    /// Determines whether this importer can handle the given input string or payload.
+    func canImport(_ input: String) -> Bool
+    
+    /// Parses the raw input string/JSON into a `MonsterViewModel`.
+    func parse(_ input: String) throws -> MonsterViewModel
+}
+
+/// Registry type that dispatches parsing to the correct importer based on format sniffing,
+/// mirroring the Android `MonsterImportHelper` dispatcher logic.
+enum ImporterRegistry {
+    
+    private static let importers: [EntityImporter] = [
+        MonsterJsonImporter(),
+        DnDBeyondImporter(),
+        Open5eImporter(),
+        BinderImporter(),
+    ]
+    
+    /// Detects which importer handles the input and delegates parse to it.
+    @MainActor
+    static func importMonster(from input: String) -> MonsterViewModel? {
+        let trimmed = input.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty else { return nil }
+        
+        for importer in importers {
+            if importer.canImport(input) {
+                do {
+                    let monster = try importer.parse(input)
+                    return monster
+                } catch {
+                    print("Importer \(type(of: importer)) error: \(error)")
+                    continue
+                }
+            }
+        }
+        return nil
+    }
+}