Fix API offset limit 400 Bad Request, implement requested UI/UX improvements

src/Predictalytics.Infrastructure/Data/Repositories/JobRepository.cs

@@ -0,0 +1,55 @@
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.EntityFrameworkCore;
+using Predictalytics.Domain.Entities;
+using Predictalytics.Domain.Enums;
+using Predictalytics.Domain.Interfaces;
+
+namespace Predictalytics.Infrastructure.Data.Repositories;
+
+public class JobRepository : IJobRepository
+{
+    private readonly AppDbContext _db;
+
+    public JobRepository(AppDbContext db)
+    {
+        _db = db;
+    }
+
+    public async Task<BackgroundJob?> GetByIdAsync(int id, CancellationToken ct = default)
+    {
+        return await _db.BackgroundJobs.Include(j => j.Trader).FirstOrDefaultAsync(j => j.Id == id, ct);
+    }
+
+    public async Task<IReadOnlyList<BackgroundJob>> GetAllAsync(int skip = 0, int take = 50, CancellationToken ct = default)
+    {
+        return await _db.BackgroundJobs
+            .Include(j => j.Trader)
+            .OrderByDescending(j => j.CreatedAt)
+            .Skip(skip)
+            .Take(take)
+            .ToListAsync(ct);
+    }
+
+    public async Task<BackgroundJob?> GetNextPendingJobAsync(JobType type, CancellationToken ct = default)
+    {
+        return await _db.BackgroundJobs
+            .Where(j => j.JobType == type && j.Status == JobStatus.Pending)
+            .OrderBy(j => j.CreatedAt)
+            .FirstOrDefaultAsync(ct);
+    }
+
+    public async Task AddAsync(BackgroundJob job, CancellationToken ct = default)
+    {
+        _db.BackgroundJobs.Add(job);
+        await _db.SaveChangesAsync(ct);
+    }
+
+    public async Task UpdateAsync(BackgroundJob job, CancellationToken ct = default)
+    {
+        _db.BackgroundJobs.Update(job);
+        await _db.SaveChangesAsync(ct);
+    }
+}

src/Predictalytics.Infrastructure/Data/Repositories/MarketRepository.cs

@@ -141,8 +141,8 @@ public class MarketRepository : IMarketRepository
 
                     if (existingEventsMap.TryGetValue(ev.PlatformEventId, out var existing))
                     {
-                        existing.Slug = ev.Slug;
-                        existing.Title = ev.Title;
+                        existing.Slug = ev.Slug!;
+                        existing.Title = ev.Title!;
                         existing.Description = ev.Description;
                         existing.ImageUrl = ev.ImageUrl;
                         existing.Tags = ev.Tags;
@@ -164,7 +164,7 @@ public class MarketRepository : IMarketRepository
                             else
                             {
                                 market.EventId = existing.Id;
-                                market.Event = null; // Prevent EF tracking issue
+                                market.Event = null!; // Prevent EF tracking issue
                                 existing.Markets.Add(market);
                             }
                         }

src/Predictalytics.Infrastructure/Data/Repositories/TraderRepository.cs

@@ -2,6 +2,7 @@ using Predictalytics.Domain.Entities;
 using Predictalytics.Domain.Enums;
 using Predictalytics.Domain.Interfaces;
 using Microsoft.EntityFrameworkCore;
+using System.Text;
 
 namespace Predictalytics.Infrastructure.Data.Repositories;
 
@@ -65,7 +66,29 @@ public class TraderRepository : ITraderRepository
     { _db.Traders.Add(trader); await _db.SaveChangesAsync(ct); }
 
     public async Task UpdateAsync(Trader trader, CancellationToken ct = default)
-    { _db.Traders.Update(trader); await _db.SaveChangesAsync(ct); }
+    {
+        _db.Traders.Update(trader);
+        await _db.SaveChangesAsync(ct);
+    }
+
+    public async Task UpdateRanksAsync(IEnumerable<(int TraderId, int Rank)> ranks, CancellationToken ct = default)
+    {
+        // Batch update ranks using raw SQL to avoid N+1 and loading entities
+        var sql = new StringBuilder();
+        sql.AppendLine("UPDATE TraderScores SET Rank = CASE TraderId");
+        var ids = new List<int>();
+        foreach (var r in ranks)
+        {
+            sql.AppendLine($"WHEN {r.TraderId} THEN {r.Rank}");
+            ids.Add(r.TraderId);
+        }
+        sql.AppendLine("ELSE Rank END WHERE TraderId IN (" + string.Join(",", ids) + ");");
+        
+        if (ids.Count > 0)
+        {
+            await _db.Database.ExecuteSqlRawAsync(sql.ToString(), ct);
+        }
+    }
 
     public async Task DeleteAsync(int id, CancellationToken ct = default)
     {