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.Core/DTOs/AiCategorizationDtos.cs

@@ -0,0 +1,49 @@
+using Purrse.Core.Enums;
+
+namespace Purrse.Core.DTOs;
+
+// Settings
+public record AiCategorizationSettingsResponse(
+    bool IsEnabled,
+    string OllamaUrl,
+    string ModelName,
+    double ConfidenceThreshold,
+    int TimeoutSeconds,
+    bool UpdatePayeeDefaults);
+
+public record UpdateAiCategorizationSettingsRequest(
+    bool IsEnabled,
+    string OllamaUrl,
+    string ModelName,
+    double ConfidenceThreshold,
+    int TimeoutSeconds,
+    bool UpdatePayeeDefaults);
+
+// Connection test
+public record OllamaConnectionTestResponse(
+    bool Success,
+    string? ErrorMessage,
+    List<string>? AvailableModels);
+
+// Ollama API communication (internal)
+public record OllamaChatRequest(string Model, List<OllamaChatMessage> Messages, bool Stream, string Format);
+public record OllamaChatMessage(string Role, string Content);
+public record OllamaChatResponse(OllamaChatMessage? Message, bool Done);
+public record OllamaTagsResponse(List<OllamaModelInfo>? Models);
+public record OllamaModelInfo(string Name, string? Model);
+
+// Classify uncategorized (manual trigger from Transactions screen)
+public record ClassifyUncategorizedRequest(
+    Guid? AccountId,
+    DateTime? StartDate,
+    DateTime? EndDate,
+    string? SearchText,
+    TransactionStatus? Status);
+
+public record ClassifyUncategorizedResponse(
+    int TotalUncategorized,
+    int Classified,
+    int Skipped);
+
+// Classification result
+public record TransactionClassification(int TransactionIndex, Guid? CategoryId, string? CategoryName, double Confidence);

src/Purrse.Core/Interfaces/Services/IAiCategorizationService.cs

@@ -0,0 +1,13 @@
+using Purrse.Core.DTOs;
+using Purrse.Core.Models;
+
+namespace Purrse.Core.Interfaces.Services;
+
+public interface IAiCategorizationService
+{
+    Task<AiCategorizationSettingsResponse> GetSettingsAsync(Guid userId);
+    Task<AiCategorizationSettingsResponse> UpdateSettingsAsync(Guid userId, UpdateAiCategorizationSettingsRequest request);
+    Task<OllamaConnectionTestResponse> TestConnectionAsync(Guid userId);
+    Task<List<TransactionClassification>> ClassifyTransactionsAsync(Guid userId, List<Transaction> uncategorizedTransactions);
+    Task<ClassifyUncategorizedResponse> ClassifyUncategorizedAsync(Guid userId, ClassifyUncategorizedRequest request);
+}

src/Purrse.Core/Models/AiCategorizationSettings.cs

@@ -0,0 +1,16 @@
+namespace Purrse.Core.Models;
+
+public class AiCategorizationSettings
+{
+    public Guid Id { get; set; }
+    public Guid UserId { get; set; }
+    public bool IsEnabled { get; set; }
+    public string OllamaUrl { get; set; } = "http://localhost:11434";
+    public string ModelName { get; set; } = "llama3.1:8b";
+    public double ConfidenceThreshold { get; set; } = 0.7;
+    public int TimeoutSeconds { get; set; } = 30;
+    public bool UpdatePayeeDefaults { get; set; } = true;
+    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
+
+    public User User { get; set; } = null!;
+}

src/Purrse.Core/Models/User.cs

@@ -14,4 +14,5 @@ public class User
     public ICollection<Account> Accounts { get; set; } = new List<Account>();
     public ICollection<SyncConnection> SyncConnections { get; set; } = new List<SyncConnection>();
     public BankSyncSettings? BankSyncSettings { get; set; }
+    public AiCategorizationSettings? AiCategorizationSettings { get; set; }
 }