feat(arena-colosseum): playable bracket + rank-match promotion (phase 2)

Closes 4 more arena-colosseum spec shapes (6/16 → 10/16): the dual-prefix
battle URLs (colosseum_battle/* and colosseum_rank_battle/*) for both
do_matching and per-match finish, plus the bracket-end /finish + /retire
pair on /arena_colosseum.

* ColosseumProgressionService: pure-logic decisions for win-threshold
  advancement, 3008 promotion trigger, and per-round reward bundles.
  Extends ColosseumRoundsConfig with FinishRewards/RetireRewards per
  round + a top-level ChampionRewards list.
* MatchContextBuilder.BuildForColosseumAsync: lifts the registered deck
  via IDeckRepository (NOT viewer-graph) per project_ef_nav_include_pitfall.
* ArenaColosseumBattleController: dual route prefixes off one controller
  via explicit absolute [HttpPost("/...")] routes — does NOT extend
  SVSimController's [Route("[controller]")]. Same pattern as FreeBattle.
  URL-vs-IsRankMatching mismatch returns 400 with a phase-mismatch error;
  no-deck triggers the standard 3001 matchmaking-illegal state. 3008
  flips run.IsRankMatching exactly once via the progression service.
* /arena_colosseum/finish + /retire share FinishResponse (rewards +
  reward_list + colosseum_status). Champion finish appends ChampionRewards
  and surfaces colosseum_status.is_champion = true. Both delete the run
  row after granting via IInventoryTransaction.GrantAsync.
* DI: ModePolicy entries for "colosseum_battle" and "colosseum_rank_battle".
* Tests: 8 progression-service unit tests (pure logic), 5 battle-controller
  HTTP tests, 5 bracket-terminate HTTP tests, 2 full-bracket E2E walks
  (champion path + retire mid-round). Full suite: 1331/1331.

SVSim.Database/Models/Config/ColosseumRoundsConfig.cs

@@ -1,7 +1,10 @@
+using SVSim.Database.Enums;
+
 namespace SVSim.Database.Models.Config;
 
 /// <summary>
-/// The 3-round bracket schedule for an active Colosseum season. Empty <see cref="Rounds"/>
+/// The 3-round bracket schedule for an active Colosseum season — and the per-round
+/// reward bundles paid out by <c>/finish</c> + <c>/retire</c>. Empty <see cref="Rounds"/>
 /// is the default shipped state — lobby <c>/event_info</c> renders a benign payload with
 /// no rounds active. Collection default is in <see cref="ShippedDefaults"/> per
 /// feedback_config_defaults (property-initializer collection defaults silently empty out
@@ -12,9 +15,14 @@ public class ColosseumRoundsConfig
 {
     public List<RoundEntry> Rounds { get; set; } = new();
 
+    /// <summary>Champion-only reward bundle, paid alongside the final round's FinishRewards
+    /// when <c>ColosseumProgressionService</c> determines the viewer cleared the bracket.</summary>
+    public List<RewardEntry> ChampionRewards { get; set; } = new();
+
     public static ColosseumRoundsConfig ShippedDefaults() => new()
     {
         Rounds = new(),
+        ChampionRewards = new(),
     };
 
     public class RoundEntry
@@ -29,6 +37,15 @@ public class ColosseumRoundsConfig
         /// for late-joiners). The first entry is the canonical lookup used by
         /// <c>ColosseumProgressionService</c> for the v1 single-bracket case.</summary>
         public List<GroupEntry> Groups { get; set; } = new();
+
+        /// <summary>Paid by <c>/finish</c> when the viewer clears or otherwise ends this round
+        /// successfully. Empty = no bonus for this round.</summary>
+        public List<RewardEntry> FinishRewards { get; set; } = new();
+
+        /// <summary>Paid by <c>/retire</c> when the viewer abandons mid-round. Client ignores
+        /// these once <c>run.RoundId &gt;= FinalB</c>, but server still emits them per
+        /// retire.md (log completeness).</summary>
+        public List<RewardEntry> RetireRewards { get; set; } = new();
     }
 
     public class GroupEntry
@@ -44,4 +61,15 @@ public class ColosseumRoundsConfig
         /// <summary>Total bracket entries allotted to this group.</summary>
         public int EntryNumber { get; set; }
     }
+
+    public class RewardEntry
+    {
+        public UserGoodsType Type { get; set; }
+        public long DetailId { get; set; }
+        public int Count { get; set; }
+
+        /// <summary>Display name for the <c>rewards[]</c> receipt block. Defaults to empty;
+        /// client uses system-text lookups when blank.</summary>
+        public string Name { get; set; } = "";
+    }
 }