Initial commit: Predictalytics solution

Clean Architecture .NET 8 solution (Domain/Application/Infrastructure/Api/Worker/WinFormsHost)
for analyzing Polymarket traders for copytrading/strategy-replication candidates.

Includes EF Core InitialBaseline migration and DB secrets removed from source/config
in preparation for version control.

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

@@ -0,0 +1,26 @@
+using Predictalytics.Domain.Entities;
+using Predictalytics.Domain.Interfaces;
+using Microsoft.EntityFrameworkCore;
+
+namespace Predictalytics.Infrastructure.Data.Repositories;
+
+public class WatchlistRepository : IWatchlistRepository
+{
+    private readonly AppDbContext _db;
+    public WatchlistRepository(AppDbContext db) => _db = db;
+
+    public async Task<IReadOnlyList<WatchlistEntry>> GetAllAsync(CancellationToken ct = default)
+        => await _db.WatchlistEntries.Include(w => w.Trader).ToListAsync(ct);
+
+    public async Task<WatchlistEntry?> GetByTraderIdAsync(int traderId, CancellationToken ct = default)
+        => await _db.WatchlistEntries.FirstOrDefaultAsync(w => w.TraderId == traderId, ct);
+
+    public async Task AddAsync(WatchlistEntry entry, CancellationToken ct = default)
+    { _db.WatchlistEntries.Add(entry); await _db.SaveChangesAsync(ct); }
+
+    public async Task RemoveAsync(int id, CancellationToken ct = default)
+    {
+        var e = await _db.WatchlistEntries.FindAsync(new object[] { id }, ct);
+        if (e != null) { _db.WatchlistEntries.Remove(e); await _db.SaveChangesAsync(ct); }
+    }
+}