feat: 完成 N 群組 — 後日談模式

錨定點抵達已出版內容盡頭時切入後日談區間；時間流速（即時同步/緩速/凍結，
另加一個非文件既定的 FAST 選項供一般角色使用）對後日談推演成年角色強制
上限 1:1，重用 L 群組 RomanceEligibilityService 的 isEpilogueAdult 判斷。
性格漂移僅在正史已有 >=2 筆 PersonalityTraitSnapshot 建立趨勢時才位移，
無證據則鎖定 0（不憑空轉向），原型字串本身從不被觸碰。人生階段推演與
角色群同步成長重用 M 群組的 Scene/ProjectionService（推演事件其實就是
sourceType=EPILOGUE 的場景，在場者投影後自然敘述互相呼應）；重大轉折
需要正史目標關鍵字對應才生成，並以 EpilogueMilestoneLog 節流頻率。
正史回收（移除被取代的推演場景、匯入官方新場景並強制投影、互動記憶
結構性保留、記憶修正事件敘事化消化）與分支保留（永久標記、擋下後續
回收）。

修正兩個真實 bug：reclaim 原本借用 importScene 的錨定閥門，導致回收
回來的正史內容反而不被投影（後日談的『現在』本來就走在錨定點之前）；
分支保留擋下重新匯入時用裸 Error 導致 500，改為 ConflictException。

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

prisma/migrations/20260813090238_add_epilogue_mode/migration.sql

@@ -0,0 +1,32 @@
+-- CreateTable
+CREATE TABLE "epilogue_milestone_logs" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "characterId" TEXT NOT NULL,
+    "storyOrder" INTEGER NOT NULL,
+    "label" TEXT NOT NULL,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT "epilogue_milestone_logs_characterId_fkey" FOREIGN KEY ("characterId") REFERENCES "characters" ("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+
+-- RedefineTables
+PRAGMA defer_foreign_keys=ON;
+PRAGMA foreign_keys=OFF;
+CREATE TABLE "new_works" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "title" TEXT NOT NULL,
+    "volumeProgress" TEXT,
+    "worldview" TEXT,
+    "progressAnchor" TEXT,
+    "anchorStoryOrder" INTEGER NOT NULL DEFAULT 0,
+    "inEpilogue" BOOLEAN NOT NULL DEFAULT false,
+    "epilogueStartStoryOrder" INTEGER,
+    "timeFlowMode" TEXT NOT NULL DEFAULT 'REALTIME',
+    "branchedFromCanon" BOOLEAN NOT NULL DEFAULT false,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL
+);
+INSERT INTO "new_works" ("anchorStoryOrder", "createdAt", "id", "progressAnchor", "title", "updatedAt", "volumeProgress", "worldview") SELECT "anchorStoryOrder", "createdAt", "id", "progressAnchor", "title", "updatedAt", "volumeProgress", "worldview" FROM "works";
+DROP TABLE "works";
+ALTER TABLE "new_works" RENAME TO "works";
+PRAGMA foreign_keys=ON;
+PRAGMA defer_foreign_keys=OFF;