feat: add iconSize column to ConversionJob

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

prisma/migrations/20260731101120_add_icon_size/migration.sql

@@ -0,0 +1,3 @@
+-- AlterTable
+ALTER TABLE `conversion_jobs` ADD COLUMN `icon_size` SMALLINT UNSIGNED NULL;
+

prisma/schema.prisma

@@ -29,6 +29,7 @@ model ConversionJob {
   inputSizeBytes            Int       @map("input_size_bytes") @db.UnsignedInt
   outputSizeBytes           Int?      @map("output_size_bytes") @db.UnsignedInt
   quality                   Int?      @db.UnsignedSmallInt
+  iconSize                  Int?      @map("icon_size") @db.UnsignedSmallInt
   conversionDurationSeconds Decimal?  @map("conversion_duration_seconds") @db.Decimal(10, 3)
   errorMessage              String?   @map("error_message") @db.VarChar(255)
   errorLog                  String?   @map("error_log") @db.Text