fix: move dav.Service init from auth_test to user testmain

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/handlers/user/testmain_test.go

@@ -8,6 +8,7 @@ import (
 	"testing"
 
 	"crussell/db"
+	"crussell/internal/dav"
 	"crussell/testutils/jwt"
 	"crussell/testutils/testdb"
 )
@@ -16,6 +17,7 @@ func TestMain(m *testing.M) {
 	pool := testdb.CreateTestDatabase("crussell_test_handlers_user")
 	db.Conn = db.NewPoolProxy(pool)
 	jwt.Init()
+	dav.Service = &dav.BaseService{}
 	testdb.SeedBaseline(pool)
 	code := m.Run()
 	testdb.DestroyTestDatabase(pool, "crussell_test_handlers_user")