Add Description field to job CSV import template

JobImportDto was missing Description despite Job entity having the field.
Downloadable template now includes a Description column; the importer maps
it directly to Job.Description with a fallback chain of Description ->
SpecialInstructions -> "Imported job".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Import/JobImportDto.cs

@@ -21,6 +21,11 @@ public class JobImportDto
     [Name("CustomerName")]
     public string? CustomerName { get; set; }
 
+    // Optional short label for the job (maps directly to Job.Description).
+    // When blank, the system falls back to SpecialInstructions, then "Imported job".
+    [Name("Description")]
+    public string? Description { get; set; }
+
     [Name("Status")]
     public string Status { get; set; } = "Pending";