feat(perf): 增加热查询索引审计

docs/performance.md

@@ -54,6 +54,13 @@ Run the hot-path harness against a running NestJS API:
 pnpm perf:check -- --base-url http://localhost:3001/api/v1
 ```
 
+Audit SQL plans and hot-path indexes:
+
+```bash
+pnpm perf:explain -- --dry-run
+DATABASE_URL=postgresql://postgres:postgres@localhost:5432/ftb_pm pnpm perf:explain
+```
+
 ## Hot Probes
 
 `perf-check` measures p50 and p95 latency, records HTTP status code counts, and exits non-zero when a request fails or p95 exceeds the current query budget.
@@ -68,6 +75,8 @@ pnpm perf:check -- --base-url http://localhost:3001/api/v1
 
 The medium fixture is the V2.6 acceptance target. Large fixture runs are for index audit and explain-plan work, not for every local commit.
 
+See `docs/performance-hot-queries.md` for query budgets, partition-key contracts, and required indexes.
+
 ## Notes
 
 - `seed-large-dataset` uses deterministic IDs and dates so repeated runs are comparable.