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.Infrastructure/Services/CsvImportService.cs

@@ -262,6 +262,7 @@ public class CsvImportService : ICsvImportService
             JobNumber = "JOB-2601-0001",
             CustomerEmail = "customer@example.com",
             CustomerName = "Acme Corp (used if email is blank or not found)",
+            Description = "Sample job description",
             Status = "Pending",
             Priority = "Normal",
             ScheduledDate = DateTime.Today.AddDays(7),
@@ -269,7 +270,7 @@ public class CsvImportService : ICsvImportService
             FinalPrice = 750.00m,
             CustomerPO = "PO-12345",
             SpecialInstructions = "Handle with care",
-            Notes = "Sample job"
+            Notes = "Internal notes"
         });
         csv.NextRecord();
 
@@ -1435,7 +1436,9 @@ public class CsvImportService : ICsvImportService
                         CustomerPO = record.CustomerPO?.Trim(),
                         SpecialInstructions = record.SpecialInstructions?.Trim(),
                         InternalNotes = record.Notes?.Trim(),
-                        Description = record.SpecialInstructions?.Trim() ?? "Imported job",
+                        Description = record.Description?.Trim()
+                            ?? record.SpecialInstructions?.Trim()
+                            ?? "Imported job",
                         CreatedAt = DateTime.UtcNow,
                         UpdatedAt = DateTime.UtcNow
                     };