refactor: Round 53 remove all legacy backward-compatibility code

- QuestSO: remove giverNpcId, prerequisiteQuests/Flags/FlagsLogic, failCondition,
  conditionFlags, npcDialogueKey fields; simplify GiverNpcId property to giverNpc?.npcId;
  clean ValidatePrerequisiteCycles/HasPrerequisiteCycle to use prerequisites.questDependencies;
  remove ValidateBranchDialogueKeys migration warning block; clean QuestPrerequisite doc
- QuestManager: remove OnLoad DataVersion 1/2 migration paths (ProgressCounts, hasNewFormat/
  useNewFormat); remove CheckQuestDepsAndFlags old-field fallback (prerequisiteQuests/Flags);
  remove UnlockBranches conditionFlags fallback; remove DispatchEvent failCondition fallback;
  fix ValidatePrerequisites DFS to scan prerequisites.questDependencies
- SaveData: remove ProgressCounts (Obsolete), ObjectiveIndex (unused), GiverNpcId (never
  written) fields from QuestState; simplify DataVersion doc comment
- QuestSOEditor: replace migration-only editor with minimal DrawDefaultInspector
- QuestModule: update all prerequisiteQuests/conditionFlags/npcDialogueKey/failCondition
  references to canonical new fields; update ValidateBranchFlags check 10
- FlagAuditModule: replace conditionFlags/prerequisiteFlags scans with conditionFlagEntries/
  prerequisites.flagCondition.flags
- NpcSO: remove QuestSO.giverNpcId reference from npcId tooltip
- NpcAffinityEvent/RewardSO: update doc comments to reference giverNpc instead of giverNpcId

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Assets/_Game/Scripts/Quest/RewardSO.cs

@@ -25,7 +25,7 @@ namespace BaseGames.Quest
         public string[] itemIds;
 
         [Header("NPC 关系")]
-        [Tooltip("完成任务后对 giverNpcId（QuestSO 中配置）的好感度增量。\n" +
+        [Tooltip("完成任务后对发布 NPC（QuestSO.giverNpc）的好感度增量。\n" +
                  "正值=好感增加，负值=好感降低。0 = 不影响好感度。\n" +
                  "增量以强类型 NpcAffinityEvent（npcId + delta + newTotal）广播至 EVT_NpcAffinityChanged，\n" +
                  "并持久化到 SaveData.World.NpcRelations。接收方无需字符串解析。")]