Remove unnecessary comments from codebase

Clean up obvious and redundant comments that don't add value:
- Remove step-by-step comments in command handlers
- Remove obvious test setup comments
- Keep only meaningful comments that explain why, not what

internal/application/commands/unmark_habit_test.go

@@ -119,7 +119,6 @@ func TestUnmarkHabitHandler_ReturnsErrorWhenEntryNotFound(t *testing.T) {
 		habitToReturn: habit,
 	}
 
-	// No entries
 	entryRepo := &mockEntryRepoForUnmark{
 		entries: []*entities.HabitEntry{},
 	}