Add rework pricing type (Fixed vs Per-Item) and inline rework flow on Job Details

Adds a PricingType enum to ReworkRecord (FixedPrice | PerItem), surfaces the
choice in the rework modal on Job Details, and wires the resulting unit/total
price display. Includes migration AddReworkPricingType, updated repository
query for rework history, and help article updates.

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

src/PowderCoating.Infrastructure/Repositories/JobRepository.cs

@@ -187,6 +187,14 @@ public class JobRepository : Repository<Job>, IJobRepository
             .FirstOrDefaultAsync();
     }
 
+    /// <inheritdoc/>
+    public async Task<int> GetReworkJobCountAsync(int originalJobId)
+    {
+        return await _context.Jobs
+            .IgnoreQueryFilters()
+            .CountAsync(j => j.OriginalJobId == originalJobId);
+    }
+
     /// <inheritdoc/>
     public async Task<List<Job>> GetOverdueScheduledJobsAsync()
     {