feat(guild_chat): deck + replay attachments

Implement all five guild_chat attachment endpoints:
- add_deck: server looks up deck by (viewerId, format, deckNo) and snapshots
  the current state into a DECK-type chat message DeckPayload column.
- delete_deck: author OR leader/sub-leader may clear; returns refreshed
  deck_log. Extended IGuildChatMessageRepository.ClearDeckAsync with
  leaderOverride flag; added GetDeckMessagesAsync + GetByMessageIdAsync.
- add_replay: stores {"battle_id": N} in ReplayPayload; full shape is
  TODO(post-merge) pending replay-subsystem capture.
- replay_detail: returns the stored ReplayPayload as JsonElement passthrough.
- deck_log: returns all active DECK messages grouped by API-side Format string
  key ("1"=Rotation, "2"=Unlimited, "3"=PreRotation always present;
  "4"=Crossover, "5"=MyRotation only when non-empty).

Adds DeckLogDataDto (typed) for deck_log / delete_deck responses.
Replay response uses JsonElement passthrough (TODO(post-merge)).
8 new integration tests — all green. Full suite 1530/1530 pass.

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

SVSim.Database/Repositories/Guild/GuildChatMessageRepository.cs

@@ -150,13 +150,25 @@ public sealed class GuildChatMessageRepository : IGuildChatMessageRepository
             await _db.SaveChangesAsync(ct);
     }
 
-    public async Task<bool> ClearDeckAsync(int guildId, int messageId, long callerViewerId, CancellationToken ct = default)
+    public Task<GuildChatMessage?> GetByMessageIdAsync(int guildId, int messageId, CancellationToken ct = default)
+        => _db.GuildChatMessages
+            .FirstOrDefaultAsync(m => m.GuildId == guildId && m.MessageId == messageId, ct);
+
+    public async Task<IReadOnlyList<GuildChatMessage>> GetDeckMessagesAsync(int guildId, CancellationToken ct = default)
+        => await _db.GuildChatMessages
+            .Where(m => m.GuildId == guildId
+                     && m.MessageType == GuildChatMessageType.Deck
+                     && m.DeckPayload != null)
+            .OrderBy(m => m.MessageId)
+            .ToListAsync(ct);
+
+    public async Task<bool> ClearDeckAsync(int guildId, int messageId, long callerViewerId, bool leaderOverride, CancellationToken ct = default)
     {
         var msg = await _db.GuildChatMessages
             .FirstOrDefaultAsync(m => m.GuildId == guildId && m.MessageId == messageId, ct);
 
         if (msg is null) return false;
-        if (msg.AuthorViewerId != callerViewerId) return false;
+        if (!leaderOverride && msg.AuthorViewerId != callerViewerId) return false;
         if (msg.DeckPayload is null) return false;
 
         msg.DeckPayload = null;