fix: remove media_type from usage_log SQL queries and test stubs

- Remove media_type column from all INSERT/SELECT/SCAN in usage_log_repo
- Remove media_type mock arg from request_type and integration tests
- Adjust scan stub value arrays from 47 to 46 elements

backend/internal/repository/usage_log_repo_request_type_test.go

@@ -154,7 +154,6 @@ func TestUsageLogRepositoryCreate_PersistsServiceTier(t *testing.T) {
 			sqlmock.AnyArg(),
 			log.ImageCount,
 			sqlmock.AnyArg(),
-			sqlmock.AnyArg(),
 			serviceTier,
 			sqlmock.AnyArg(),
 			sqlmock.AnyArg(),
@@ -470,7 +469,6 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			sql.NullString{},
 			0,
 			sql.NullString{},
-			sql.NullString{},
 			sql.NullString{Valid: true, String: "priority"},
 			sql.NullString{},
 			sql.NullString{},
@@ -518,7 +516,6 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			sql.NullString{},
 			0,
 			sql.NullString{},
-			sql.NullString{},
 			sql.NullString{Valid: true, String: "flex"},
 			sql.NullString{},
 			sql.NullString{},
@@ -566,7 +563,6 @@ func TestScanUsageLogRequestTypeAndLegacyFallback(t *testing.T) {
 			sql.NullString{},
 			0,
 			sql.NullString{},
-			sql.NullString{},
 			sql.NullString{Valid: true, String: "priority"},
 			sql.NullString{},
 			sql.NullString{},