feat(spot-card-exchange): /spot_card_exchange/{top,exchange} + SpotPoints currency

Final shop family. Schema additions:
- ViewerCurrency.SpotPoints (ulong) — new currency column on Viewers.
- SpotCardExchangeEntry — catalog (distinct from the pre-existing
  SpotCardEntry, which is the /load/index rental-cost concept).
- ViewerSpotCardExchange — standalone composite-PK table tracking
  (viewer, card, exchanged_at, is_pre_release_snapshot). Standalone
  avoids cartesian-explode on viewer-graph reads.

RewardGrantService gains a SpotCardPoint=12 currency case mirroring
the RedEther/Crystal pattern. Doc comment refreshed; SpotCard=11 and
SpotCardOnlyLatestCardPack=13 remain unimplemented with explanatory
NotSupportedException — captures show emitters always use Card=5 with
the spot-card-specific id.

Controller:
- /top: emits exactly 9 clan buckets [{"1": [cards]}, ...] matching
  prod's arbitrary single-key shape. exchange_status per-card (0=
  available, 1=already-exchanged, 2=LimitOver after pre-release cap).
  pre_relase_info WIRE TYPO PRESERVED ("relase" not "release").
- /exchange: server-authoritative price (client-supplied
  exchange_point ignored); debits SpotPoints with post-state-total
  reward_list entry; grants card via RewardGrantService.ApplyAsync
  (cosmetic cascade included); persists ViewerSpotCardExchange row.
  Insufficient points / already-exchanged / pre-release-limit all
  return 400 without partial state.

LoadController now populates /load/index spot_point from
viewer.Currency.SpotPoints (was always 0).

PreReleaseLimit hardcoded to 2 matching capture; promote to GameConfig
when captures show variance.

504 tests pass (was 496; +8 spot-card-exchange tests).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.Bootstrap/Importers/SpotCardExchangeImporter.cs

@@ -0,0 +1,55 @@
+using Microsoft.EntityFrameworkCore;
+using SVSim.Bootstrap.Models.Seed;
+using SVSim.Database;
+using SVSim.Database.Models;
+
+namespace SVSim.Bootstrap.Importers;
+
+/// <summary>
+/// Idempotent upsert of the spot card exchange catalog from <c>seeds/spot-card-exchange.json</c>.
+/// Source is the wire <c>/spot_card_exchange/top</c> response, extracted via
+/// <c>data_dumps/extract/extract-spot-card-exchange.py</c>. Rows missing from the seed are
+/// LEFT INTACT.
+/// </summary>
+public class SpotCardExchangeImporter
+{
+    public async Task<int> ImportAsync(SVSimDbContext context, string seedDir)
+    {
+        string path = Path.Combine(seedDir, "spot-card-exchange.json");
+        var seed = SeedLoader.LoadList<SpotCardExchangeSeed>(path);
+        if (seed.Count == 0)
+        {
+            Console.WriteLine("[SpotCardExchangeImporter] No seed rows; skipping.");
+            return 0;
+        }
+
+        var existing = await context.SpotCardExchangeCatalog.ToDictionaryAsync(e => e.Id);
+        int created = 0, updated = 0;
+
+        foreach (var s in seed)
+        {
+            if (s.CardId == 0) continue;
+
+            var entry = existing.TryGetValue(s.CardId, out var ex)
+                ? ex : new SpotCardExchangeEntry { Id = s.CardId };
+
+            entry.ClassId = s.ClassId;
+            entry.ExchangePoint = s.ExchangePoint;
+            entry.TsRotationId = s.TsRotationId;
+            entry.IsPreRelease = s.IsPreRelease;
+            entry.IsEnabled = true;
+
+            if (ex is null)
+            {
+                context.SpotCardExchangeCatalog.Add(entry);
+                existing[s.CardId] = entry;
+                created++;
+            }
+            else updated++;
+        }
+
+        await context.SaveChangesAsync();
+        Console.WriteLine($"[SpotCardExchangeImporter] +{created}/~{updated}");
+        return created + updated;
+    }
+}

SVSim.Bootstrap/Models/Seed/SpotCardExchangeSeed.cs

@@ -0,0 +1,12 @@
+using System.Text.Json.Serialization;
+
+namespace SVSim.Bootstrap.Models.Seed;
+
+public sealed class SpotCardExchangeSeed
+{
+    [JsonPropertyName("card_id")] public long CardId { get; set; }
+    [JsonPropertyName("class")] public int ClassId { get; set; }
+    [JsonPropertyName("exchange_point")] public int ExchangePoint { get; set; }
+    [JsonPropertyName("ts_rotation_id")] public long TsRotationId { get; set; }
+    [JsonPropertyName("is_pre_release")] public bool IsPreRelease { get; set; }
+}

SVSim.Bootstrap/Program.cs

@@ -101,6 +101,7 @@ public static class Program
             await new SleeveShopImporter().ImportAsync(context, opts.SeedDir);
             await new ItemPurchaseImporter().ImportAsync(context, opts.SeedDir);
             await new LeaderSkinShopImporter().ImportAsync(context, opts.SeedDir);
+            await new SpotCardExchangeImporter().ImportAsync(context, opts.SeedDir);
             var puzzleImporter = new PuzzleImporter();
             await puzzleImporter.ImportGroupsAsync(context, opts.SeedDir);
             await puzzleImporter.ImportPuzzlesAsync(context, opts.SeedDir);