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/Controllers/ProductController.cs

@@ -0,0 +1,71 @@
+using Microsoft.AspNetCore.Mvc;
+using RR3CommunityServer.Models;
+using RR3CommunityServer.Services;
+
+namespace RR3CommunityServer.Controllers;
+
+[ApiController]
+[Route("product/api/core")]
+public class ProductController : ControllerBase
+{
+    private readonly ICatalogService _catalogService;
+    private readonly ILogger<ProductController> _logger;
+
+    public ProductController(ICatalogService catalogService, ILogger<ProductController> logger)
+    {
+        _catalogService = catalogService;
+        _logger = logger;
+    }
+
+    [HttpGet("getAvailableItems")]
+    public async Task<ActionResult<SynergyResponse<List<CatalogItem>>>> GetAvailableItems()
+    {
+        _logger.LogInformation("GetAvailableItems request");
+
+        var items = await _catalogService.GetAvailableItems();
+
+        var response = new SynergyResponse<List<CatalogItem>>
+        {
+            resultCode = 0,
+            message = "Success",
+            data = items
+        };
+
+        return Ok(response);
+    }
+
+    [HttpGet("getMTXGameCategories")]
+    public async Task<ActionResult<SynergyResponse<List<CatalogCategory>>>> GetCategories()
+    {
+        _logger.LogInformation("GetMTXGameCategories request");
+
+        var categories = await _catalogService.GetCategories();
+
+        var response = new SynergyResponse<List<CatalogCategory>>
+        {
+            resultCode = 0,
+            message = "Success",
+            data = categories
+        };
+
+        return Ok(response);
+    }
+
+    [HttpPost("getDownloadItemUrl")]
+    public async Task<ActionResult<SynergyResponse<object>>> GetDownloadUrl([FromBody] Dictionary<string, string> request)
+    {
+        var itemId = request.GetValueOrDefault("itemId", "");
+        _logger.LogInformation("GetDownloadItemUrl: {ItemId}", itemId);
+
+        var url = await _catalogService.GetDownloadUrl(itemId);
+
+        var response = new SynergyResponse<object>
+        {
+            resultCode = 0,
+            message = "Success",
+            data = new { downloadUrl = url }
+        };
+
+        return Ok(response);
+    }
+}