feat(models): add Asset/ChatTurn, indicator-report relationship, pinned flag

按 W2 plan Task 2 落地数据模型:
- Indicator 加 report / asset / pinned 字段
- Report 加 indicators / assets @Relationship(cascade)
- DiaryEntry 加 tags
- 新增 @Model Asset (原图元数据)
- 新增 @Model ChatTurn (问答历史 + 引用)
- TijiApp Schema 加入新 model

注:Schema 破坏性变更,用户需在 Xcode 里 Erase Simulator
后重启 App。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

体己/App/TijiApp.swift

@@ -8,6 +8,8 @@ struct TijiApp: App {
             Indicator.self,
             Report.self,
             DiaryEntry.self,
+            Asset.self,
+            ChatTurn.self,
         ])
         let config = ModelConfiguration(schema: schema, isStoredInMemoryOnly: false)
         do {