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/Controllers/AiCategorizationController.cs

@@ -0,0 +1,34 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Purrse.Core.DTOs;
+using Purrse.Core.Interfaces.Services;
+using System.Security.Claims;
+
+namespace Purrse.Api.Controllers;
+
+[Authorize]
+[ApiController]
+[Route("api/ai-categorization")]
+public class AiCategorizationController : ControllerBase
+{
+    private readonly IAiCategorizationService _aiService;
+    private Guid UserId => Guid.Parse(User.FindFirstValue(ClaimTypes.NameIdentifier)!);
+
+    public AiCategorizationController(IAiCategorizationService aiService) => _aiService = aiService;
+
+    [HttpGet("settings")]
+    public async Task<ActionResult<AiCategorizationSettingsResponse>> GetSettings()
+        => Ok(await _aiService.GetSettingsAsync(UserId));
+
+    [HttpPut("settings")]
+    public async Task<ActionResult<AiCategorizationSettingsResponse>> UpdateSettings(UpdateAiCategorizationSettingsRequest request)
+        => Ok(await _aiService.UpdateSettingsAsync(UserId, request));
+
+    [HttpPost("test-connection")]
+    public async Task<ActionResult<OllamaConnectionTestResponse>> TestConnection()
+        => Ok(await _aiService.TestConnectionAsync(UserId));
+
+    [HttpPost("classify")]
+    public async Task<ActionResult<ClassifyUncategorizedResponse>> ClassifyUncategorized(ClassifyUncategorizedRequest request)
+        => Ok(await _aiService.ClassifyUncategorizedAsync(UserId, request));
+}