test: improve test coverage from 11% to 20%

Add comprehensive tests across multiple packages:

- mhfpacket: Add tests for 300+ packet opcodes, system packets,
  MHF packets, and detailed parsing tests (6.4% -> 38.8%)
- timeserver: Add tests for all time functions (0% -> 97.4%)
- deltacomp: Add edge case tests for compression functions
- entranceserver: Add server creation tests
- binpacket: Add mail notify panic test
- config: Add Mode.String() tests
- signserver: Expand server tests

server/channelserver/timeserver/time_mode_test.go

@@ -0,0 +1,150 @@
+package timeserver
+
+import (
+	"testing"
+	"time"
+)
+
+func TestPFaddTime(t *testing.T) {
+	// Save original state
+	originalPnewtime := Pnewtime
+	defer func() { Pnewtime = originalPnewtime }()
+
+	Pnewtime = 0
+
+	// First call should return 24
+	result := PFadd_time()
+	if result != time.Duration(24) {
+		t.Errorf("PFadd_time() = %v, want 24", result)
+	}
+
+	// Second call should return 48
+	result = PFadd_time()
+	if result != time.Duration(48) {
+		t.Errorf("PFadd_time() second call = %v, want 48", result)
+	}
+
+	// Check Pfixtimer is updated
+	if Pfixtimer != time.Duration(48) {
+		t.Errorf("Pfixtimer = %v, want 48", Pfixtimer)
+	}
+}
+
+func TestTimeCurrent(t *testing.T) {
+	result := TimeCurrent()
+	if result.IsZero() {
+		t.Error("TimeCurrent() returned zero time")
+	}
+
+	// Result should be in the past (7 years ago)
+	now := time.Now()
+	diff := now.Year() - result.Year()
+	if diff != 7 {
+		t.Errorf("TimeCurrent() year diff = %d, want 7", diff)
+	}
+}
+
+func TestTimeMidnight(t *testing.T) {
+	result := Time_midnight()
+	if result.IsZero() {
+		t.Error("Time_midnight() returned zero time")
+	}
+
+	// Result should be midnight (with hour added, so 1:00 AM)
+	if result.Minute() != 0 {
+		t.Errorf("Time_midnight() minute = %d, want 0", result.Minute())
+	}
+	if result.Second() != 0 {
+		t.Errorf("Time_midnight() second = %d, want 0", result.Second())
+	}
+}
+
+func TestTimeStatic(t *testing.T) {
+	// Reset state for testing
+	DoOnce_t = false
+	Fix_t = time.Time{}
+
+	result := Time_static()
+	if result.IsZero() {
+		t.Error("Time_static() returned zero time")
+	}
+
+	// Calling again should return same time (static)
+	result2 := Time_static()
+	if !result.Equal(result2) {
+		t.Error("Time_static() should return same time on second call")
+	}
+}
+
+func TestTstaticMidnight(t *testing.T) {
+	// Reset state for testing
+	DoOnce_midnight = false
+	Fix_midnight = time.Time{}
+
+	result := Tstatic_midnight()
+	if result.IsZero() {
+		t.Error("Tstatic_midnight() returned zero time")
+	}
+
+	// Calling again should return same time (static)
+	result2 := Tstatic_midnight()
+	if !result.Equal(result2) {
+		t.Error("Tstatic_midnight() should return same time on second call")
+	}
+}
+
+func TestTimeCurrentWeekUint8(t *testing.T) {
+	result := Time_Current_Week_uint8()
+
+	// Week of month should be 1-5
+	if result < 1 || result > 5 {
+		t.Errorf("Time_Current_Week_uint8() = %d, expected 1-5", result)
+	}
+}
+
+func TestTimeCurrentWeekUint32(t *testing.T) {
+	result := Time_Current_Week_uint32()
+
+	// Week of month should be 1-5
+	if result < 1 || result > 5 {
+		t.Errorf("Time_Current_Week_uint32() = %d, expected 1-5", result)
+	}
+}
+
+func TestDetectDay(t *testing.T) {
+	result := Detect_Day()
+
+	// Result should be bool, and true only on Wednesday
+	isWednesday := time.Now().Weekday() == time.Wednesday
+	if result != isWednesday {
+		t.Errorf("Detect_Day() = %v, expected %v (today is %v)", result, isWednesday, time.Now().Weekday())
+	}
+}
+
+func TestGlobalVariables(t *testing.T) {
+	// Test that global variables exist and have expected default types
+	_ = DoOnce_midnight
+	_ = DoOnce_t2
+	_ = DoOnce_t
+	_ = Fix_midnight
+	_ = Fix_t2
+	_ = Fix_t
+	_ = Pfixtimer
+	_ = Pnewtime
+}
+
+func TestTimeConsistency(t *testing.T) {
+	// Test that TimeCurrent and Time_midnight are on the same day
+	current := TimeCurrent()
+	midnight := Time_midnight()
+
+	if current.Year() != midnight.Year() {
+		t.Errorf("Year mismatch: current=%d, midnight=%d", current.Year(), midnight.Year())
+	}
+	if current.Month() != midnight.Month() {
+		t.Errorf("Month mismatch: current=%v, midnight=%v", current.Month(), midnight.Month())
+	}
+	if current.Day() != midnight.Day() {
+		t.Errorf("Day mismatch: current=%d, midnight=%d", current.Day(), midnight.Day())
+	}
+}