feat: Add TTSBackendMetadata model

tests/test_tts_backend.py

@@ -0,0 +1,29 @@
+from dataclasses import dataclass
+
+from abogen.tts_backend import TTSBackendMetadata
+
+
+class TestTTSBackendMetadata:
+    def test_is_frozen_dataclass(self):
+        assert dataclass(TTSBackendMetadata)
+
+    def test_fields_are_present(self):
+        meta = TTSBackendMetadata(
+            id="test",
+            name="Test Backend",
+            description="A test backend",
+        )
+        assert meta.id == "test"
+        assert meta.name == "Test Backend"
+        assert meta.description == "A test backend"
+
+    def test_is_immutable(self):
+        import pytest
+
+        meta = TTSBackendMetadata(
+            id="kokoro",
+            name="Kokoro",
+            description="Test",
+        )
+        with pytest.raises(Exception):
+            meta.id = "changed"