[iamthebestofcourse]

Summary

astroml/db/session.py already defines PageParams/Page/paginate_offset as the standard pagination envelope (issue #948), but the two routers that envelope was designed for, astroml/api/routers/accounts.py and astroml/api/routers/fraud.py, still hand-rolled the same (items, total, page, page_size) shape and the same offset = (page - 1) * page_size math themselves, duplicating what the shared helper already does.

closes #953

Changes

• list_accounts, get_account_transactions (accounts.py), and list_fraud_alerts (fraud.py) now take page_params: PageParams = Depends() instead of separate page/page_size query params, and build their response with paginate_offset(items, total, page_params) instead of manually computing offset and constructing the response dict by hand.
• No change to the public query-parameter contract: PageParams already validates page/page_size identically (page >= 1, 1 <= page_size <= 100, defaults 1/20) to the Query(...) declarations it replaces.
• Response shape is unchanged (items, total, page, page_size).

Test plan

• Added to tests/test_pagination_envelope.py: test_paginated_endpoints_take_page_params_as_a_dependency (all three endpoints take PageParams via Depends) and test_router_modules_import_the_shared_envelope (asserts paginate_offset is used and the old (page - 1) * page_size formula is gone from both router modules). 34/34 tests in that file pass.
• black --check, ruff check: clean on both touched router files and the test file.
• mypy: identical pre-existing errors on both router files before and after this change (verified via git stash + rerun), no new errors introduced.
• Full end-to-end HTTP test of these endpoints (tests/performance/test_api_endpoints.py) requires the full requirements-api.txt dependency tree (jose, strawberry-graphql, etc.) which isn't set up in this environment; not run here, but nothing in this change touches auth, GraphQL, or request/response wire format, only the internal pagination computation.