test: add coverage tests to reach 65% total coverage

Add 16 test files across 4 packages covering previously untested
handler paths: guild board operations, house/warehouse management,
tower/tenrouirai progress, diva schedule, festa info, cafe duration,
API error paths, sign server responses, and byteframe boundaries.

server/channelserver/handlers_quest_coverage_test.go

@@ -0,0 +1,40 @@
+package channelserver
+
+import (
+	"testing"
+
+	"erupe-ce/network/mhfpacket"
+)
+
+func TestHandleMsgMhfLoadFavoriteQuest(t *testing.T) {
+	server := createMockServer()
+	server.charRepo = newMockCharacterRepo()
+	session := createMockSession(100, server)
+
+	pkt := &mhfpacket.MsgMhfLoadFavoriteQuest{AckHandle: 1}
+	handleMsgMhfLoadFavoriteQuest(session, pkt)
+
+	select {
+	case <-session.sendPackets:
+	default:
+		t.Error("expected response")
+	}
+}
+
+func TestHandleMsgMhfSaveFavoriteQuest(t *testing.T) {
+	server := createMockServer()
+	server.charRepo = newMockCharacterRepo()
+	session := createMockSession(100, server)
+
+	pkt := &mhfpacket.MsgMhfSaveFavoriteQuest{
+		AckHandle: 1,
+		Data:      []byte{0x01, 0x00, 0x01, 0x00, 0x01},
+	}
+	handleMsgMhfSaveFavoriteQuest(session, pkt)
+
+	select {
+	case <-session.sendPackets:
+	default:
+		t.Error("expected response")
+	}
+}