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_festa_info_coverage_test.go

@@ -0,0 +1,52 @@
+package channelserver
+
+import (
+	cfg "erupe-ce/config"
+	"erupe-ce/network/mhfpacket"
+	"testing"
+	"time"
+)
+
+func TestHandleMsgMhfInfoFesta_OverrideZero(t *testing.T) {
+	srv := createMockServer()
+	srv.festaRepo = &mockFestaRepo{}
+	srv.erupeConfig.DebugOptions.FestaOverride = 0
+	s := createMockSession(100, srv)
+
+	pkt := &mhfpacket.MsgMhfInfoFesta{AckHandle: 1}
+	handleMsgMhfInfoFesta(s, pkt)
+	<-s.sendPackets
+}
+
+func TestHandleMsgMhfInfoFesta_WithActiveEvent(t *testing.T) {
+	srv := createMockServer()
+	srv.erupeConfig.DebugOptions.FestaOverride = 1
+	srv.erupeConfig.RealClientMode = cfg.ZZ
+	srv.erupeConfig.GameplayOptions.MaximumFP = 50000
+	srv.festaRepo = &mockFestaRepo{
+		events: []FestaEvent{{ID: 1, StartTime: uint32(time.Now().Add(-24 * time.Hour).Unix())}},
+		trials: []FestaTrial{
+			{ID: 1, Objective: 1, GoalID: 100, TimesReq: 5, Locale: 0, Reward: 10, Monopoly: "blue"},
+		},
+	}
+	ensureFestaService(srv)
+	s := createMockSession(100, srv)
+
+	pkt := &mhfpacket.MsgMhfInfoFesta{AckHandle: 1}
+	handleMsgMhfInfoFesta(s, pkt)
+	<-s.sendPackets
+}
+
+func TestHandleMsgMhfInfoFesta_FutureTimestamp(t *testing.T) {
+	srv := createMockServer()
+	srv.erupeConfig.DebugOptions.FestaOverride = -1
+	srv.festaRepo = &mockFestaRepo{
+		events: []FestaEvent{{ID: 1, StartTime: uint32(time.Now().Add(72 * time.Hour).Unix())}},
+	}
+	ensureFestaService(srv)
+	s := createMockSession(100, srv)
+
+	pkt := &mhfpacket.MsgMhfInfoFesta{AckHandle: 1}
+	handleMsgMhfInfoFesta(s, pkt)
+	<-s.sendPackets
+}