Sweep kiosk intake submission for FK/null bugs

- Fix Jobs.Id FK violation: save job first with CompleteAsync() to get
  its DB-assigned Id, THEN set session.LinkedJobId and save again.
  Previously job.Id was still 0 when written to the nullable FK column.
- Replace ?? 1 fallbacks on JobStatusId/JobPriorityId with explicit
  InvalidOperationException — hardcoded 1 may not exist in the company's
  lookup tables; now fails loud with a clear message instead of an FK error.
- Add ValidateSessionState check to Terms POST so expired/already-submitted
  sessions don't re-run ProcessSubmissionAsync and create duplicate jobs.
- Null-guard session.JobDescription before slicing for notification snippet.
- Tighten catch block: wrap the fallback CompleteAsync in its own try/catch
  so a secondary failure doesn't mask the original error in logs.
- Swap Job.Description / SpecialInstructions: Description now holds the
  actual job description text; SpecialInstructions records the intake source.

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

src/PowderCoating.Web/Controllers/KioskController.cs

@@ -394,6 +394,9 @@ public class KioskController : Controller
         var session = await LoadSessionAsync(token);
         if (session == null) return View("KioskError", "Session not found.");
 
+        // Expired/already-submitted sessions go straight to Confirmation
+        if (!await ValidateSessionState(session)) return RedirectToAction(nameof(Confirmation), new { token });
+
         // Require signature for in-person sessions
         if (session.SessionType == KioskSessionType.InPerson &&
             string.IsNullOrEmpty(dto.SignatureDataBase64))
@@ -423,8 +426,9 @@ public class KioskController : Controller
         catch (Exception ex)
         {
             _logger.LogError(ex, "Error processing kiosk submission for session {SessionToken}", token);
-            // Don't fail the customer-facing page — save what we have and let staff convert manually
-            await _unitOfWork.CompleteAsync();
+            // Customer-facing page always succeeds — staff can convert the session manually.
+            // Persist the session's agreed/submitted state even if job creation failed.
+            try { await _unitOfWork.CompleteAsync(); } catch { /* best-effort */ }
         }
 
         return RedirectToAction(nameof(Confirmation), new { token });
@@ -589,9 +593,14 @@ public class KioskController : Controller
         // 3. Create Job in Pending status with Normal priority
         var statuses      = await _lookupCache.GetJobStatusLookupsAsync(companyId);
         var pendingStatus = statuses.FirstOrDefault(s => s.StatusCode == AppConstants.StatusCodes.Job.Pending);
+        if (pendingStatus == null)
+            throw new InvalidOperationException($"No Pending job status found for company {companyId}. Run Seed Data from Platform Management.");
 
         var priorities     = await _lookupCache.GetJobPriorityLookupsAsync(companyId);
-        var normalPriority = priorities.FirstOrDefault(p => p.PriorityCode == "NORMAL") ?? priorities.FirstOrDefault();
+        var normalPriority = priorities.FirstOrDefault(p => p.PriorityCode == "NORMAL")
+                          ?? priorities.FirstOrDefault();
+        if (normalPriority == null)
+            throw new InvalidOperationException($"No job priority rows found for company {companyId}. Run Seed Data from Platform Management.");
 
         var jobNumber = await GenerateJobNumberAsync(companyId);
         var job = new Job
@@ -599,29 +608,27 @@ public class KioskController : Controller
             CompanyId           = companyId,
             CustomerId          = customer!.Id,
             JobNumber           = jobNumber,
-            JobStatusId         = pendingStatus?.Id ?? 1,
-            JobPriorityId       = normalPriority?.Id ?? 1,
-            SpecialInstructions = session.JobDescription,
-            Description         = $"Walk-in intake — {session.CustomerFirstName} {session.CustomerLastName}".Trim()
+            JobStatusId         = pendingStatus.Id,
+            JobPriorityId       = normalPriority.Id,
+            Description         = session.JobDescription,
+            SpecialInstructions = $"Source: {session.SessionType} kiosk intake"
         };
 
         await _unitOfWork.Jobs.AddAsync(job);
 
-        // 4. Update session links
-        session.LinkedCustomerId = customer.Id;
-        session.LinkedJobId      = job.Id;   // will be populated after SaveChanges below
+        // Save the job first so EF generates its Id, then link the session.
+        // Setting session.LinkedJobId = job.Id before CompleteAsync would write 0
+        // to the FK column because the DB hasn't assigned the Id yet.
+        await _unitOfWork.CompleteAsync();  // job.Id is now valid
 
+        // 4. Update session links now that both Ids exist
+        session.LinkedCustomerId = customer.Id;
+        session.LinkedJobId      = job.Id;
         await _unitOfWork.CompleteAsync();
 
-        // job.Id is now set — update session again if needed
-        if (session.LinkedJobId == 0)
-        {
-            session.LinkedJobId = job.Id;
-            await _unitOfWork.CompleteAsync();
-        }
-
         // 5. Fire staff notification
-        var snippet  = session.JobDescription.Length > 60 ? session.JobDescription[..60] + "…" : session.JobDescription;
+        var jobDesc  = session.JobDescription ?? "";
+        var snippet  = jobDesc.Length > 60 ? jobDesc[..60] + "…" : jobDesc;
         var fullName = $"{session.CustomerFirstName} {session.CustomerLastName}".Trim();
         await _inApp.CreateAsync(
             companyId,