Fix AI price check truncation and JSON parse errors

Root cause: MaxTokens=4096 was too low — 25 items at ~250 tokens each hit the
limit mid-array (logged error showed Path: $[17]).

- MaxTokens: 4096 → 8192
- BatchSize: 25 → 15 items (keeps each response well under the limit)
- StripJsonFences → ExtractJsonArray: now also handles prose before/after the
  JSON array, and recovers truncated responses by finding the last complete
  object and closing the array — so partial batches return whatever Claude
  finished rather than nothing
- GET action: added try-catch around ResultsJson deserialization so a bad DB
  row shows a friendly "re-run" warning instead of a raw error page

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

src/PowderCoating.Web/Controllers/CatalogItemsController.cs

@@ -944,9 +944,19 @@ namespace PowderCoating.Web.Controllers
             CatalogPriceCheckReportDto? dto = null;
             if (report != null)
             {
-                var results = JsonSerializer.Deserialize<List<CatalogItemPriceVerdict>>(
-                    report.ResultsJson,
-                    new JsonSerializerOptions { PropertyNameCaseInsensitive = true }) ?? new();
+                List<CatalogItemPriceVerdict> results;
+                try
+                {
+                    results = JsonSerializer.Deserialize<List<CatalogItemPriceVerdict>>(
+                        report.ResultsJson,
+                        new JsonSerializerOptions { PropertyNameCaseInsensitive = true }) ?? new();
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogError(ex, "Failed to deserialize stored price check report {ReportId}", report.Id);
+                    TempData["Warning"] = "The previous report could not be loaded. Please re-run the price check.";
+                    results = new();
+                }
 
                 dto = new CatalogPriceCheckReportDto
                 {