Add AI categorization with Ollama: settings, auto-classify on sync/import, and manual classify from Transactions

Adds local LLM-based transaction categorization using Ollama:
- Settings UI to configure Ollama URL, model, confidence threshold
- Auto-categorization during bank sync and file import
- Manual "Classify Uncategorized" button on Transactions screen that respects active filters
- Payee default category learning loop for classified transactions

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

src/Purrse.Api/Services/BankSyncService.cs

@@ -20,6 +20,7 @@ public class BankSyncService : IBankSyncService
     private readonly SimpleFinSyncProvider _simpleFin;
     private readonly IDuplicateDetectionService _duplicateService;
     private readonly IPayeeService _payeeService;
+    private readonly IAiCategorizationService _aiCategorization;
     private readonly IHubContext<NotificationHub> _hub;
     private readonly ILogger<BankSyncService> _logger;
 
@@ -30,6 +31,7 @@ public class BankSyncService : IBankSyncService
         SimpleFinSyncProvider simpleFin,
         IDuplicateDetectionService duplicateService,
         IPayeeService payeeService,
+        IAiCategorizationService aiCategorization,
         IHubContext<NotificationHub> hub,
         ILogger<BankSyncService> logger)
     {
@@ -39,6 +41,7 @@ public class BankSyncService : IBankSyncService
         _simpleFin = simpleFin;
         _duplicateService = duplicateService;
         _payeeService = payeeService;
+        _aiCategorization = aiCategorization;
         _hub = hub;
         _logger = logger;
     }
@@ -500,6 +503,39 @@ public class BankSyncService : IBankSyncService
             }
         }
 
+        // AI auto-categorization for uncategorized transactions
+        try
+        {
+            var uncategorized = _db.ChangeTracker.Entries<Transaction>()
+                .Where(e => e.State == EntityState.Added && e.Entity.CategoryId == null)
+                .Select(e => e.Entity)
+                .ToList();
+
+            if (uncategorized.Count > 0)
+            {
+                var classifications = await _aiCategorization.ClassifyTransactionsAsync(userId, uncategorized);
+                foreach (var c in classifications)
+                {
+                    if (c.CategoryId.HasValue && c.TransactionIndex >= 0 && c.TransactionIndex < uncategorized.Count)
+                    {
+                        uncategorized[c.TransactionIndex].CategoryId = c.CategoryId.Value;
+
+                        var txn = uncategorized[c.TransactionIndex];
+                        if (txn.PayeeId.HasValue)
+                        {
+                            var payee = await _db.Payees.FindAsync(txn.PayeeId.Value);
+                            if (payee != null && payee.DefaultCategoryId == null)
+                                payee.DefaultCategoryId = c.CategoryId.Value;
+                        }
+                    }
+                }
+            }
+        }
+        catch (Exception ex)
+        {
+            _logger.LogWarning(ex, "AI categorization failed during sync, continuing without");
+        }
+
         connection.LastSyncAt = DateTime.UtcNow;
         connection.LastSyncError = accountResults.Any(r => r.Error != null)
             ? accountResults.First(r => r.Error != null).Error