fix(promo-codes): address CodeRabbit findings — CSV domain import and migration rollback

CodeRabbit flagged 6 issues on PR #525. After independent validation (Codex),
2 were confirmed as real bugs, 2 were false positives, and 2 were
informational/misframed.

Fixed (validated as real):
- **CSV import TypeError:** `allowed_email_domains` was not exploded from its
  pipe-delimited CSV string before reaching `setAllowedEmailDomains(array)`,
  causing a TypeError on domain-authorized code import. Added the same
  `explode('|', ...)` normalization used by all other CSV list fields in both
  the add and update import paths.
- **Migration down() failure:** Dropping the joined domain-authorized tables
  did not remove orphaned base-table rows, so narrowing the ClassName ENUM
  would fail if any domain-authorized promo codes existed. Added a DELETE
  statement before the ALTER TABLE.

Dismissed (validated as false positives):
- `remaining_quantity_per_account = null` in MemberDiscountCode serializer is
  correct — Member types do not have per-account quantity.
- Discover route already has OAuth2 auth via the `api` middleware group and
  an explicit controller-level null-member guard. Adding `auth.user` would
  break it (requires authz_groups, intentionally removed in 138c1f8).

Deferred:
- `boolval("false")` pattern is pre-existing across the factory (not
  introduced by this PR); warrants a separate cleanup.
- Multi-level TLD validation regex (`.co.uk`) is an enhancement, not a bug
  in the current domain-matching logic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: caseylocker

app/Services/Model/Imp/SummitPromoCodeService.php

@@ -642,6 +642,10 @@ public function importPromoCodes(Summit $summit, UploadedFile $csv_file, ?Member
                     $row['tags'] = explode('|', $row['tags']);
                 }
 
+                if(isset($row['allowed_email_domains'])){
+                    $row['allowed_email_domains'] = explode('|', $row['allowed_email_domains']);
+                }
+
                 if(isset($row['ticket_types_rules']) && (isset($row['amount']) || isset($row['rate']))){
 
                     $row['ticket_types_rules'] = explode('|', $row['ticket_types_rules']);
@@ -745,6 +749,10 @@ public function importSponsorPromoCodes(Summit $summit, UploadedFile $csv_file,
                     $row['tags'] = explode('|', $row['tags']);
                 }
 
+                if(isset($row['allowed_email_domains'])){
+                    $row['allowed_email_domains'] = explode('|', $row['allowed_email_domains']);
+                }
+
                 if(isset($row['ticket_types_rules']) && (isset($row['amount']) || isset($row['rate']))){
 
                     $row['ticket_types_rules'] = explode('|', $row['ticket_types_rules']);

database/migrations/model/Version20260401150000.php

@@ -100,6 +100,12 @@ public function down(Schema $schema): void
         $this->addSql("DROP TABLE IF EXISTS DomainAuthorizedSummitRegistrationPromoCode");
         $this->addSql("DROP TABLE IF EXISTS DomainAuthorizedSummitRegistrationDiscountCode");
 
+        // 4b. Delete orphaned base-table rows before narrowing the ENUM
+        $this->addSql("DELETE FROM SummitRegistrationPromoCode WHERE ClassName IN (
+            'DomainAuthorizedSummitRegistrationDiscountCode',
+            'DomainAuthorizedSummitRegistrationPromoCode'
+        )");
+
         // 5. Revert the ClassName discriminator ENUM to the original 12 values
         $this->addSql("ALTER TABLE SummitRegistrationPromoCode MODIFY ClassName ENUM(
             'SummitRegistrationPromoCode',