feat(bp): repositories + identity generation for runtime-inserted tables

Add ValueGeneratedOnAdd to ViewerBattlePassProgress.Id and
ViewerBattlePassClaims.Id so Postgres generates IDENTITY values at
runtime. Regenerate AddBattlePass migration in-place to include the
IdentityByDefaultColumn annotations. Add IBattlePassRepository /
BattlePassRepository (season lookup + level-curve cache) and
IViewerBattlePassRepository / ViewerBattlePassRepository
(get-or-create progress, claim reads/writes).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.Database/Repositories/BattlePass/ViewerBattlePassRepository.cs

@@ -0,0 +1,45 @@
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.BattlePass;
+
+public sealed class ViewerBattlePassRepository : IViewerBattlePassRepository
+{
+    private readonly SVSimDbContext _db;
+
+    public ViewerBattlePassRepository(SVSimDbContext db) { _db = db; }
+
+    public async Task<ViewerBattlePassProgressEntry> GetOrCreateProgressAsync(long viewerId, int seasonId, CancellationToken ct)
+    {
+        var existing = await _db.ViewerBattlePassProgress
+            .FirstOrDefaultAsync(p => p.ViewerId == viewerId && p.SeasonId == seasonId, ct);
+        if (existing is not null) return existing;
+
+        var entry = new ViewerBattlePassProgressEntry
+        {
+            ViewerId = viewerId,
+            SeasonId = seasonId,
+            CurrentPoint = 0,
+            IsPremium = false,
+            WeeklyPoints = 0,
+            WeeklyPeriodStart = null,
+        };
+        _db.ViewerBattlePassProgress.Add(entry);
+        return entry;
+    }
+
+    public Task<List<ViewerBattlePassClaimEntry>> GetClaimsAsync(long viewerId, int seasonId, CancellationToken ct) =>
+        _db.ViewerBattlePassClaims.AsNoTracking()
+            .Where(c => c.ViewerId == viewerId && c.SeasonId == seasonId)
+            .ToListAsync(ct);
+
+    public void AddClaim(long viewerId, int seasonId, BattlePassTrack track, int level, DateTimeOffset claimedAt)
+    {
+        _db.ViewerBattlePassClaims.Add(new ViewerBattlePassClaimEntry
+        {
+            ViewerId = viewerId, SeasonId = seasonId, Track = track,
+            Level = level, ClaimedAt = claimedAt,
+        });
+    }
+}