Fix database bugs and add comprehensive test report 🔧📋

Bugs Fixed:
- Fixed SQLite missing column errors (Cash, Gold, Level, etc.)
- Fixed LINQ translation error in AssetsController (File.Exists)
- Fixed type mismatch in ModdingController (null coalescing)
- Applied database migrations for complete schema

Database Changes:
- Added User currency columns (Gold, Cash, Level, XP, Reputation)
- Added Car custom content fields (IsCustom, CustomAuthor, CustomVersion)
- Added GameAsset metadata fields (Md5Hash, CompressedSize)
- Added ModPacks table for mod bundling

Testing:
- Comprehensive test report: COMPREHENSIVE_TEST_REPORT.md
- 9/9 critical endpoints passing
- All APK-required functionality verified
- Database operations validated
- Response format compatibility confirmed

Status: ✅ Server is production-ready (pending assets)

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

RR3CommunityServer/Controllers/ModdingController.cs

@@ -272,7 +272,13 @@ public class ModdingController : ControllerBase
         {
             success = true,
             count = content.Count,
-            content = content
+            content = content.Select(c => new
+            {
+                id = c.id,
+                author = c.author,
+                type = c.type,
+                files = c.files.ToList()
+            }).ToList()
         });
     }
 
@@ -371,8 +377,8 @@ public class ModdingController : ControllerBase
             Author = request.Author,
             Description = request.Description,
             Version = request.Version ?? "1.0",
-            CarIds = string.Join(",", request.CarIds ?? Array.Empty<string>()),
-            TrackIds = string.Join(",", request.TrackIds ?? Array.Empty<string>()),
+            CarIds = request.CarIds != null ? string.Join(",", request.CarIds) : string.Empty,
+            TrackIds = request.TrackIds != null ? string.Join(",", request.TrackIds) : string.Empty,
             CreatedAt = DateTime.UtcNow
         };
 
@@ -396,26 +402,28 @@ public class ModdingController : ControllerBase
     public async Task<IActionResult> GetModPacks()
     {
         var packs = await _context.ModPacks
-            .Select(p => new
+            .ToListAsync();
+        
+        var result = packs.Select(p => new
             {
                 packId = p.PackId,
                 name = p.Name,
                 author = p.Author,
                 description = p.Description,
                 version = p.Version,
-                carCount = p.CarIds != null ? p.CarIds.Split(',').Length : 0,
-                trackCount = p.TrackIds != null ? p.TrackIds.Split(',').Length : 0,
+                carCount = !string.IsNullOrEmpty(p.CarIds) ? p.CarIds.Split(',').Length : 0,
+                trackCount = !string.IsNullOrEmpty(p.TrackIds) ? p.TrackIds.Split(',').Length : 0,
                 downloads = p.DownloadCount,
                 rating = p.Rating,
                 createdAt = p.CreatedAt
             })
-            .ToListAsync();
+            .ToList();
 
         return Ok(new
         {
             success = true,
-            count = packs.Count,
-            modPacks = packs
+            count = result.Count,
+            modPacks = result
         });
     }