feat(status): 启用 pg_stat_statements,运行状态页显示最慢 / 最频繁语句与各表死元组;PG 调低 random_page_cost

- docker-compose.yml 的 postgres 加 shared_preload_libraries=pg_stat_statements、pg_stat_statements.track=top;
  要重建 postgres 容器才生效(docs/runbook/storage.md)
- GET /system/storage 的 db.statements:平均最慢(调用 ≥ 10 次)与调用最多各 5 条;没装扩展 / 没预加载时
  enabled=false 并说明原因
- 运行状态页「存储」:体积最大的表加死元组列,新增「数据库语句统计」
- random_page_cost 4 → 1.1(PG_RANDOM_PAGE_COST):库整个在内存里,缺省值高估随机读

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Cxwgnn2pbzQ7rXv3rq7fei

apps/web/app/components/status/storage-section.tsx

@@ -200,6 +200,72 @@ function CleanupTable({ rows }: { rows: CleanupRow[] }) {
 }
 
 /** 运行状态页的「存储」节 */
+type Statements = SystemStorage["db"]["statements"];
+type StatementRow = Statements["slowest"][number];
+
+const fmtMs = (ms: number) =>
+  ms >= 1000 ? `${(ms / 1000).toFixed(1)} 秒` : `${ms < 10 ? ms.toFixed(2) : Math.round(ms)} 毫秒`;
+
+function StatementTable({ rows }: { rows: StatementRow[] }) {
+  return (
+    <DataTable<StatementRow>
+      rows={rows}
+      rowKey={(r) => r.query}
+      empty={{ title: "还没有统计" }}
+      columns={[
+        {
+          key: "query",
+          header: "语句",
+          cell: (r) => (
+            <span className="line-clamp-2 font-mono text-meta break-all" title={r.query}>
+              {r.query}
+            </span>
+          ),
+        },
+        {
+          key: "calls",
+          header: "次数",
+          align: "right",
+          cell: (r) => <span className="tabular-nums">{r.calls.toLocaleString("zh-CN")}</span>,
+        },
+        {
+          key: "mean",
+          header: "平均",
+          align: "right",
+          cell: (r) => <span className="whitespace-nowrap tabular-nums">{fmtMs(r.meanMs)}</span>,
+        },
+        {
+          key: "total",
+          header: "合计",
+          align: "right",
+          hideBelow: "sm",
+          cell: (r) => <span className="whitespace-nowrap tabular-nums text-muted-foreground">{fmtMs(r.totalMs)}</span>,
+        },
+      ]}
+    />
+  );
+}
+
+/** 数据库语句统计(pg_stat_statements,见 docs/runbook/storage.md「数据库性能」) */
+function StatementsInfo({ st }: { st: Statements }) {
+  return (
+    <TechInfo title="数据库语句统计" columns={1}>
+      {st.enabled ? (
+        <div className="grid gap-6 xl:grid-cols-2">
+          <Panel title="平均最慢" note={`调用 10 次以上${st.since ? ` · 统计自 ${formatDateTime(st.since)}` : ""}`}>
+            <StatementTable rows={st.slowest} />
+          </Panel>
+          <Panel title="调用最多">
+            <StatementTable rows={st.frequent} />
+          </Panel>
+        </div>
+      ) : (
+        <p className="text-caption text-muted-foreground">语句统计未启用：{st.note}</p>
+      )}
+    </TechInfo>
+  );
+}
+
 export function StorageSection({ health }: { health: SystemHealth }) {
   const q = useSystemStorage();
   const s = q.data;
@@ -305,6 +371,17 @@ export function StorageSection({ health }: { health: SystemHealth }) {
                         </span>
                       ),
                     },
+                    {
+                      key: "dead",
+                      header: "死元组",
+                      align: "right",
+                      hideBelow: "md",
+                      cell: (t) => (
+                        <span className="tabular-nums text-muted-foreground">
+                          {t.deadRows === null ? "—" : t.deadRows.toLocaleString("zh-CN")}
+                        </span>
+                      ),
+                    },
                   ]}
                 />
               </Panel>
@@ -391,6 +468,8 @@ export function StorageSection({ health }: { health: SystemHealth }) {
             </div>
           </div>
 
+          <StatementsInfo st={s.db.statements} />
+
           <Panel title="清理任务" note="立即清理会把对应的维护任务排入执行，结果看运行记录">
             <CleanupTable rows={s.cleanup} />
           </Panel>