[BUG] — `ApiServiceImpl.listByPage`: N+1 + no SQL pagination + selects large `document` TEXT

- severity: High; files: `ApiServiceImpl.java:261-273`; SQL `mappers/api-sqlmap.xml:268-301`
- description: (1) `ApiServiceImpl` has no `@Pageable` (verified 0 occurrences); `PageResultUtils.result(pageParameter, listSupplier)` (2-arg form, `PageResultUtils.java:55-57`) applies no SQL LIMIT — full result set loaded. (2) Per-row N+1: `tagRelationMapper.selectByQuery(apiId)` then `tagMapper.selectByIds(tagIds)` per API; `tag_relation` has no index on `api_id`/`tag_id`. (3) List selects `api.document` (LONGVARCHAR/TEXT) for every row though a list view does not need it.
- impact: Unbounded memory + row count × 2 round-trips; can OOM/stall on large inventories.
- suggested_fix: Add `@Pageable`; exclude `document` from the list column list; batch-fetch tag relations for all page ids in one query.
- confidence: High

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_Identified during the 2026-08-02 deep re-scan; full list in [`docs/scan2-2026-08-02/00-consolidated-critical-high.md`](docs/scan2-2026-08-02/00-consolidated-critical-high.md)._

Start with ApiServiceImpl.java:261-273, mappers/api-sqlmap.xml:268-301, and PageResultUtils.java:55-57 to trace list construction, pagination, and tag lookups. Done means the list query applies SQL pagination, omits the document column, and tag relations and tags are fetched in batches for the page IDs without per-row lookups.

Written by the indexing model from the issue text.