Fix file upload stale reference and improve company matching

File upload fix:
- Buffer file data immediately on selection to prevent stale IBrowserFile references
- Add BufferedFile record to hold file data in memory
- Add loading indicator while files are being buffered
- Fixes "Cannot read properties of null (reading '_blazorFilesById')" error

Company matching improvement:
- Prefer companies that existed at the claimed employment start date
- Fixes matching wrong company when newer company has similar name
- Example: "UK MATTEL LTD" (2025) vs "MATTEL U.K. LIMITED" (1980)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/TrueCV.Infrastructure/Services/CompanyVerifierService.cs

@@ -70,8 +70,8 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
                 return CreateUnverifiedResult(companyName, startDate, endDate, jobTitle, "No matching company found in Companies House");
             }
 
-            // Find best fuzzy match
-            var bestMatch = FindBestMatch(companyName, searchResponse.Items);
+            // Find best fuzzy match, preferring companies that existed at claimed start date
+            var bestMatch = FindBestMatch(companyName, searchResponse.Items, startDate);
 
             if (bestMatch is null)
             {
@@ -560,7 +560,8 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
 
     private static (CompaniesHouseSearchItem Item, int Score)? FindBestMatch(
         string companyName,
-        List<CompaniesHouseSearchItem> items)
+        List<CompaniesHouseSearchItem> items,
+        DateOnly? claimedStartDate)
     {
         var normalizedSearch = companyName.ToUpperInvariant();
 
@@ -568,10 +569,32 @@ public sealed class CompanyVerifierService : ICompanyVerifierService
             .Where(item => !string.IsNullOrWhiteSpace(item.Title))
             .Select(item => (Item: item, Score: Fuzz.TokenSetRatio(normalizedSearch, item.Title.ToUpperInvariant())))
             .Where(m => m.Score >= FuzzyMatchThreshold)
-            .OrderByDescending(m => m.Score)
             .ToList();
 
-        return matches.Count > 0 ? matches[0] : null;
+        if (matches.Count == 0) return null;
+
+        // If we have a claimed start date, prefer companies that existed at that time
+        if (claimedStartDate.HasValue)
+        {
+            var existedAtStartDate = matches
+                .Where(m =>
+                {
+                    var incDate = DateHelpers.ParseDate(m.Item.DateOfCreation);
+                    // Company existed if it was incorporated before the claimed start date
+                    return incDate == null || incDate <= claimedStartDate.Value;
+                })
+                .OrderByDescending(m => m.Score)
+                .ToList();
+
+            // If any matches existed at the start date, prefer those
+            if (existedAtStartDate.Count > 0)
+            {
+                return existedAtStartDate[0];
+            }
+        }
+
+        // Fall back to highest score if no temporal match
+        return matches.OrderByDescending(m => m.Score).First();
     }
 
     private async Task CacheCompanyAsync(CompaniesHouseSearchItem item, CompaniesHouseCompany? details)