fix(server): restore achievements, progress, claims and experience

Load ordinary achievements and send transactional gameplay progress notifications.
Restore main-story clears and recorded gacha history without duplicate credit.
Validate claim thresholds and prior tiers, credit wallet rewards and persist
achievement experience in login responses.

go/internal/server/protocol/protocol_test.go

@@ -25,6 +25,27 @@ func TestEncode(t *testing.T) {
 	}
 }
 
+func TestNotifyIsPlainBase64SeparateFromEncryptedResponse(t *testing.T) {
+	key := []byte("0123456789abcdef0123456789abcdef")
+	notify := []byte{0x12, 6, 8, 42, 16, 7, 24, 1}
+	raw, err := EncodeWithNotify(167, nil, key, 123, notify)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var envelope Envelope
+	if err := json.Unmarshal(raw, &envelope); err != nil {
+		t.Fatal(err)
+	}
+	decoded, err := base64.StdEncoding.DecodeString(envelope.Notify)
+	if err != nil || string(decoded) != string(notify) {
+		t.Fatalf("notify=%x err=%v", decoded, err)
+	}
+	response, err := cryptox.DecryptBase64Payload(envelope.Data, key)
+	if err != nil || len(response) != 0 {
+		t.Fatalf("response=%x err=%v", response, err)
+	}
+}
+
 func TestBatchPreservesOrderAndRejectsDuplicates(t *testing.T) {
 	key := []byte("0123456789abcdef0123456789abcdef")
 	input := []BatchRequest{{Path: "/B", RequestData: base64.StdEncoding.EncodeToString([]byte{8, 1})}, {Path: "/A", RequestData: base64.StdEncoding.EncodeToString([]byte{8, 2})}}