Initial commit: RR3 Community Server with web admin panel

- ASP.NET Core 8 REST API server
- 12 API endpoints matching EA Synergy protocol
- SQLite database with Entity Framework Core
- Web admin panel with Bootstrap 5
- User, Catalog, Session, Purchase management
- Comprehensive documentation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

RR3CommunityServer/Pages/Purchases.cshtml.cs

@@ -0,0 +1,52 @@
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.EntityFrameworkCore;
+using RR3CommunityServer.Data;
+using static RR3CommunityServer.Data.RR3DbContext;
+
+namespace RR3CommunityServer.Pages;
+
+public class PurchasesModel : PageModel
+{
+    private readonly RR3DbContext _context;
+
+    public PurchasesModel(RR3DbContext context)
+    {
+        _context = context;
+    }
+
+    public List<Purchase> Purchases { get; set; } = new();
+    public decimal TotalValue { get; set; }
+    public string? SearchQuery { get; set; }
+
+    public async Task OnGetAsync(string? search)
+    {
+        SearchQuery = search;
+        
+        var query = _context.Purchases.AsQueryable();
+        
+        if (!string.IsNullOrEmpty(search))
+        {
+            query = query.Where(p => p.Sku.Contains(search) || 
+                                     (p.UserId != null && p.UserId.ToString()!.Contains(search)));
+        }
+        
+        Purchases = await query
+            .OrderByDescending(p => p.PurchaseDate)
+            .ToListAsync();
+
+        TotalValue = Purchases.Sum(p => p.Price);
+    }
+
+    public async Task<IActionResult> OnPostDeleteAsync(int purchaseId)
+    {
+        var purchase = await _context.Purchases.FindAsync(purchaseId);
+        if (purchase != null)
+        {
+            _context.Purchases.Remove(purchase);
+            await _context.SaveChangesAsync();
+        }
+
+        return RedirectToPage();
+    }
+}