perf(storage): 拦截任务二进制并本地暂存结果

原因：任务标准结果中的 Base64、Data URI 和 Buffer 会进入 PostgreSQL JSON，导致 TOAST 与备份体积快速增长。

影响：新增统一 JSON 持久化关口；upload_none 将二进制原子写入本地结果目录，数据库仅保存带 SHA-256 的有界占位符；任务详情、同步响应、异步查询和兼容协议按需校验恢复。补充 24 小时清理、容量上限、历史小批量治理命令及管理端说明。

风险：本地结果超过 TTL、丢失或损坏时分别返回明确的 410/500；空间不足时返回 503 且不重试上游。未自动执行历史治理。

验证：三种真实图片模型同步/异步与幂等重放通过；Go vet/全量测试、前端 111 测试、lint/typecheck/build、OpenAPI、迁移安全、govulncheck、依赖审计、手工发布测试及 Linux amd64 构建通过。

apps/api/internal/store/binary_result_backfill.go

@@ -0,0 +1,87 @@
+package store
+
+import (
+	"context"
+	"encoding/json"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+)
+
+type TaskBinaryResultBackfillItem struct {
+	ID         string
+	Result     map[string]any
+	FinishedAt time.Time
+}
+
+func (s *Store) ListTaskBinaryResultBackfillBatch(ctx context.Context, afterID string, batchSize int) ([]TaskBinaryResultBackfillItem, error) {
+	if batchSize < 1 || batchSize > 100 {
+		batchSize = 100
+	}
+	var items []TaskBinaryResultBackfillItem
+	err := pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `SET LOCAL lock_timeout = '5s'; SET LOCAL statement_timeout = '5s'`); err != nil {
+			return err
+		}
+		rows, err := tx.Query(ctx, `
+SELECT id::text, result, COALESCE(finished_at, updated_at)
+FROM gateway_tasks
+WHERE status = 'succeeded'
+  AND result <> '{}'::jsonb
+  AND (NULLIF($1::text, '') IS NULL OR id > NULLIF($1::text, '')::uuid)
+ORDER BY id
+LIMIT $2`, afterID, batchSize)
+		if err != nil {
+			return err
+		}
+		defer rows.Close()
+		items = make([]TaskBinaryResultBackfillItem, 0, batchSize)
+		for rows.Next() {
+			var item TaskBinaryResultBackfillItem
+			var resultJSON []byte
+			if err := rows.Scan(&item.ID, &resultJSON, &item.FinishedAt); err != nil {
+				return err
+			}
+			item.Result = decodeObject(resultJSON)
+			items = append(items, item)
+		}
+		return rows.Err()
+	})
+	return items, err
+}
+
+func (s *Store) UpdateTaskBinaryResultBackfill(ctx context.Context, taskID string, result map[string]any) (bool, error) {
+	report := sanitizeJSONForStorageWithReport(minimalTaskResult(result))
+	if report.BinaryCount > 0 {
+		return false, &taskPayloadBinaryError{
+			target: ErrTaskResultBinaryNotMaterialized,
+			code:   "result_binary_not_materialized",
+			count:  report.BinaryCount,
+		}
+	}
+	resultJSON, err := json.Marshal(report.Value)
+	if err != nil {
+		return false, err
+	}
+	updated := false
+	err = pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+		if _, err := tx.Exec(ctx, `SET LOCAL lock_timeout = '5s'; SET LOCAL statement_timeout = '5s'`); err != nil {
+			return err
+		}
+		tag, err := tx.Exec(ctx, `
+UPDATE gateway_tasks
+SET result = $2::jsonb,
+    updated_at = now()
+WHERE id = $1::uuid
+  AND status = 'succeeded'`,
+			taskID,
+			string(resultJSON),
+		)
+		if err != nil {
+			return err
+		}
+		updated = tag.RowsAffected() == 1
+		return nil
+	})
+	return updated, err
+}