Add quote-changed banner with re-sync to job details

When a source quote is edited after a job was created from it, the job
details page now shows a warning banner with the date of the change and
a link to the quote. Two actions are offered:

- Re-sync from Quote: replaces all job items, coats, prep services, and
  pricing from the current quote. Only available while the job is still
  in a pre-production status (Pending, Quoted, Approved); hidden once
  shop work has started (InPreparation or beyond).
- Dismiss: acknowledges the change without altering the job, clearing
  the banner by advancing the stored snapshot timestamp.

Implemented via Job.QuoteSnapshotUpdatedAt (new nullable column), set at
quote→job conversion time. The banner fires when quote.UpdatedAt exceeds
this baseline. Migration: AddJobQuoteSnapshotUpdatedAt.

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

src/PowderCoating.Core/Entities/Job.cs

@@ -55,6 +55,10 @@ public class Job : BaseEntity
     public int? IntakePartCount { get; set; }
     public string? IntakeCheckedByUserId { get; set; }
 
+    // Quote snapshot — UpdatedAt of the source quote at the moment this job was created from it.
+    // Used to detect when the quote was subsequently edited so the job details page can warn the user.
+    public DateTime? QuoteSnapshotUpdatedAt { get; set; }
+
     // Rework tracking
     public bool IsReworkJob { get; set; }
     public int? OriginalJobId { get; set; }       // Set when this job was created as a rework