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/Admin.cshtml.cs

@@ -0,0 +1,58 @@
+using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.EntityFrameworkCore;
+using RR3CommunityServer.Data;
+using static RR3CommunityServer.Data.RR3DbContext;
+
+namespace RR3CommunityServer.Pages;
+
+public class AdminModel : PageModel
+{
+    private readonly RR3DbContext _context;
+
+    public AdminModel(RR3DbContext context)
+    {
+        _context = context;
+    }
+
+    public int TotalUsers { get; set; }
+    public int ActiveSessions { get; set; }
+    public int TotalDevices { get; set; }
+    public int TotalCatalogItems { get; set; }
+    public string Uptime { get; set; } = "0:00:00";
+    public string ServerUrl { get; set; } = string.Empty;
+    public string Platform { get; set; } = string.Empty;
+    public string DotNetVersion { get; set; } = string.Empty;
+    
+    public List<User> RecentUsers { get; set; } = new();
+    public List<Session> RecentSessions { get; set; } = new();
+
+    public async Task OnGetAsync()
+    {
+        // Get statistics
+        TotalUsers = await _context.Users.CountAsync();
+        TotalDevices = await _context.Devices.CountAsync();
+        TotalCatalogItems = await _context.CatalogItems.CountAsync();
+        ActiveSessions = await _context.Sessions
+            .Where(s => s.ExpiresAt > DateTime.UtcNow)
+            .CountAsync();
+
+        // Get recent activity
+        RecentUsers = await _context.Users
+            .OrderByDescending(u => u.CreatedAt)
+            .Take(5)
+            .ToListAsync();
+
+        RecentSessions = await _context.Sessions
+            .Where(s => s.ExpiresAt > DateTime.UtcNow)
+            .OrderByDescending(s => s.CreatedAt)
+            .Take(5)
+            .ToListAsync();
+
+        // Server info
+        var uptime = DateTime.UtcNow - System.Diagnostics.Process.GetCurrentProcess().StartTime.ToUniversalTime();
+        Uptime = $"{uptime.Days}d {uptime.Hours}h {uptime.Minutes}m";
+        ServerUrl = $"{Request.Scheme}://{Request.Host}";
+        Platform = Environment.OSVersion.Platform.ToString();
+        DotNetVersion = Environment.Version.ToString();
+    }
+}