fix: use discriminated union for backfill schema and remove duplicate comment

- Use discriminated union so transactionHash is required for mined entries
- Remove duplicated AMEX comment block

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: eabdelmoneim

src/server/routes/admin/backfill.ts

@@ -5,27 +5,26 @@ import { TransactionDB } from "../../../shared/db/transactions/db";
 import { standardResponseSchema } from "../../schemas/shared-api-schemas";
 
 // SPECIAL LOGIC FOR AMEX
-// added two admin routes to backfill tx hashes to the backfill table
-// loadBackfillRoute and clearBackfillRoute
-// loadBackfillRoute is used to load tx hashes to the backfill table
-// clearBackfillRoute is used to clear the backfill table
-// these routes are used by the AMEX script to backfill tx hashes to the backfill table
-// see https://github.com/thirdweb-dev/solutions-customer-scripts/blob/main/amex/scripts/load-backfill-via-api.ts
-// loadBackfillRoute is used to load tx hashes to the backfill table
-// clearBackfillRoute is used to clear the backfill table
-// these routes are used by the AMEX script to backfill tx hashes to the backfill table
-// see https://github.com/thirdweb-dev/solutions-customer-scripts/blob/main/amex/scripts/load-backfill-via-api.ts
+// Two admin routes to backfill transaction data:
+// - loadBackfillRoute: Load queueId to status/transactionHash mappings
+// - clearBackfillRoute: Clear all backfill entries
+// See https://github.com/thirdweb-dev/solutions-customer-scripts/blob/main/amex/scripts/load-backfill-via-api.ts
+
+const MinedEntrySchema = Type.Object({
+  queueId: Type.String({ description: "Queue ID (UUID)" }),
+  status: Type.Literal("mined"),
+  transactionHash: Type.String({ description: "Transaction hash (0x...)" }),
+});
+
+const ErroredEntrySchema = Type.Object({
+  queueId: Type.String({ description: "Queue ID (UUID)" }),
+  status: Type.Literal("errored"),
+});
 
 const loadRequestBodySchema = Type.Object({
   entries: Type.Array(
-    Type.Object({
-      queueId: Type.String({ description: "Queue ID (UUID)" }),
-      status: Type.Union([Type.Literal("mined"), Type.Literal("errored")], {
-        description: "Transaction status: 'mined' for successful transactions, 'errored' for failed ones",
-      }),
-      transactionHash: Type.Optional(
-        Type.String({ description: "Transaction hash (0x...). Required for mined transactions." }),
-      ),
+    Type.Union([MinedEntrySchema, ErroredEntrySchema], {
+      description: "Entry with status 'mined' requires transactionHash; status 'errored' does not",
     }),
     {
       description: "Array of queueId to status/transactionHash mappings",