Initial commit: Purrse personal finance app

Self-hosted, plugin-extensible personal finance manager built with
ASP.NET Core 9.0, Vue 3 + Vuetify 3, and PostgreSQL 17.

Backend (8 .NET projects):
- Core: 19 domain models, 6 enums, 14 DTOs, 12 service interfaces
- Data: EF Core DbContext, 16 entity configurations, category seeder
- API: 14 controllers, 15 services, JWT auth, SignalR, middleware
- Plugins: Abstractions + OFX/CSV/QIF file parsers
- Tests: 28 xUnit tests (fingerprinting, duplicate detection, parsers)

Frontend (Vue 3 + Vuetify 3 + TypeScript):
- 13 views, Pinia stores, Axios API services with JWT interceptors
- Dashboard, accounts, transactions, categories, imports, and more

Deployment:
- Docker Compose (PostgreSQL 17 + .NET API + nginx frontend)
- Auto-migration on startup

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

src/Purrse.Api/Hubs/NotificationHub.cs

@@ -0,0 +1,24 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.SignalR;
+
+namespace Purrse.Api.Hubs;
+
+[Authorize]
+public class NotificationHub : Hub
+{
+    public override async Task OnConnectedAsync()
+    {
+        var userId = Context.UserIdentifier;
+        if (userId != null)
+            await Groups.AddToGroupAsync(Context.ConnectionId, userId);
+        await base.OnConnectedAsync();
+    }
+
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        var userId = Context.UserIdentifier;
+        if (userId != null)
+            await Groups.RemoveFromGroupAsync(Context.ConnectionId, userId);
+        await base.OnDisconnectedAsync(exception);
+    }
+}