feat(v2.2): 建立分区关系表和AppData迁移预演

docs/architecture.md

@@ -220,3 +220,26 @@ Managers with `xiaobao.warning:manage` can see all unfinished versions. Non-mana
 AI explains rule results only. It writes interpretation cache to `xiaobao-risk-insights` and never mutates Version, Requirement, DevTask, TestCase, Bug, or Member data. Risk snapshots are saved to `xiaobao-risk-snapshots` when the page is opened. The first version uses page-triggered analysis rather than a background scheduled Agent.
 
 Per-user warning read state is saved to `xiaobao-warning-views`. The read marker stores `userId + versionId + risk signature`, so the sidebar can turn the Xiaobao badge blue when any visible risk has a completed unread update, then return to the red risk-count badge after the user opens every updated warning. AI interpretation that is still generating only shows the "updating" notice and must not produce the blue update badge yet.
+## V2.2 Partitioned Domain Data Layer (2026-07-03)
+
+V2.2 starts the move from AppData JSON documents to relation tables for high-volume domains. The first database foundation is partitioned from the start so future growth does not require a disruptive rewrite of primary keys, unique constraints, and foreign-key references.
+
+High-growth business tables use fixed hash partitions:
+
+- `requirements`: hash partitioned by `product_id`; primary key is `(id, product_id)`.
+- `dev_tasks`, `test_cases`, and `bugs`: hash partitioned by `version_id`; primary key is `(id, version_id)`.
+
+Append-only evidence and history tables use range partitions by `created_at`:
+
+- `work_activities`
+- `task_worklogs`
+- `overtime_records`
+- `xiaobao_risk_snapshots`
+- `xiaobao_risk_insights`
+- `ai_logs`
+
+Partitioned tables must include the partition key in every primary key and business unique constraint. Cross-table references to partitioned tables use composite foreign keys when the referencing row naturally carries the partition key, for example `(requirement_id, requirement_product_id)` and `(test_case_id, test_case_version_id)`. Polymorphic activity references remain logical references.
+
+Xiaobao uses two storage shapes: `xiaobao_risk_summaries` keeps one current row per version for fast reads, while `xiaobao_risk_snapshots` stores append-only history for trend analysis.
+
+The AppData migration path is staged through a pure mapper plus preview service. `AppDataV22MigrationService.preview()` reads the allowed `app_data` keys, maps legacy JSON into partition-key-ready rows, and reports row counts plus skipped records before any insert path is enabled.