test: expand channelserver coverage from 12% to 16%

Add comprehensive tests for handler files:
- handlers_object: object creation, positioning, binary ops
- handlers_semaphore: create, acquire, release, check, delete
- handlers_reserve: stub handlers and reserve188/18B
- handlers_event: registration, release, feature weapons
- handlers_mutex: create, open, close, delete operations
- handlers_campaign: enumerate, state, apply
- handlers_bbs: user status, SNS status, article apply
- handlers_tournament: info, entry, acquire
- handlers_users: user binary operations
- handlers_clients: client enumeration
- handlers_rengoku: ranking
- handlers_register: raviente semaphore functions
- handlers_tower: tower info, tenrouirai, seibatu ranking

All tests pass with race detection enabled.

server/channelserver/handlers_bbs_test.go

@@ -0,0 +1,74 @@
+package channelserver
+
+import (
+	"testing"
+
+	"erupe-ce/config"
+	"erupe-ce/network/mhfpacket"
+)
+
+func TestHandleMsgMhfGetBbsUserStatus(t *testing.T) {
+	server := createMockServer()
+	session := createMockSession(1, server)
+
+	pkt := &mhfpacket.MsgMhfGetBbsUserStatus{
+		AckHandle: 12345,
+	}
+
+	handleMsgMhfGetBbsUserStatus(session, pkt)
+
+	// Verify response packet was queued
+	select {
+	case p := <-session.sendPackets:
+		if len(p.data) == 0 {
+			t.Error("Response packet should have data")
+		}
+	default:
+		t.Error("No response packet queued")
+	}
+}
+
+func TestHandleMsgMhfGetBbsSnsStatus(t *testing.T) {
+	server := createMockServer()
+	session := createMockSession(1, server)
+
+	pkt := &mhfpacket.MsgMhfGetBbsSnsStatus{
+		AckHandle: 12345,
+	}
+
+	handleMsgMhfGetBbsSnsStatus(session, pkt)
+
+	// Verify response packet was queued
+	select {
+	case p := <-session.sendPackets:
+		if len(p.data) == 0 {
+			t.Error("Response packet should have data")
+		}
+	default:
+		t.Error("No response packet queued")
+	}
+}
+
+func TestHandleMsgMhfApplyBbsArticle(t *testing.T) {
+	server := createMockServer()
+	server.erupeConfig = &config.Config{
+		ScreenshotAPIURL: "http://example.com/api",
+	}
+	session := createMockSession(1, server)
+
+	pkt := &mhfpacket.MsgMhfApplyBbsArticle{
+		AckHandle: 12345,
+	}
+
+	handleMsgMhfApplyBbsArticle(session, pkt)
+
+	// Verify response packet was queued
+	select {
+	case p := <-session.sendPackets:
+		if len(p.data) == 0 {
+			t.Error("Response packet should have data")
+		}
+	default:
+		t.Error("No response packet queued")
+	}
+}