Extract File CRUD out of the crud/__init__.py monolith

[akwasigroch]

Purpose

crud/__init__.py is a 1946-line monolith that the codebase is splitting one entity at a time, following #2411, #2412, #2438, #2439, #2441, #2442, #2449, #2450 and #2451. This takes the File block out. Per apps/backend/AGENTS.md the package only shrinks from here — nothing new goes back into __init__.py.

What Changed

• Moved create_file, get_file, link_file_to_entity, get_files_for_entity, get_entity_files_total_size, get_entity_files_max_position and delete_file into a new crud/file.py (151 lines), unchanged. The # File CRUD operations banner in __init__.py goes with them.
• crud/__init__.py drops 121 lines.
• Nothing is re-exported, matching the earlier splits. All 27 call sites across 9 files now use from rhesis.backend.app.crud import file as file_crud.
• Nothing dropped — all seven functions have callers.
• routers/telemetry.py and routers/file.py no longer need from rhesis.backend.app import crud at all. services/invokers/tracing.py and services/telemetry/conversation_linking.py had function-local from rhesis.backend.app import crud as _crud imports, now direct submodule imports.
• Removing the block left func with no module-scope use in __init__.py, which turned the pre-existing function-local from sqlalchemy import func inside get_user_by_email into a ruff F811. func is therefore dropped from the top-level from sqlalchemy import and_, func, select, text. and_, select and text are still used.

Additional Context

• One of four parallel extractions: Behavior (Extract Behavior CRUD out of the crud/__init__.py monolith #2455), File, Model (Extract Model CRUD out of the crud/__init__.py monolith #2457) and User (Extract User CRUD out of the crud/__init__.py monolith #2458). The four blocks were chosen so they do not touch each other in crud/__init__.py, and git merge-tree confirms __init__.py merges clean across all six pairings — including the func import change above.
• This branch is conflict-free against all three siblings.
• Suggested landing order across the four: this one and Behavior first (conflict-free), then Model, then User.
• Deliberately avoids get_test_sets and get_tests, which Add metric tuning for custom metrics [feature branch] #2446 modifies.

Testing

Pure move — behaviour is unchanged, so the existing suite is the check.

cd apps/backend
uv run pytest ../../tests/backend/services/test_file_execution.py ../../tests/backend/services/test_file_integration.py ../../tests/backend/routes/test_file.py
# 35 passed

uv run pytest ../../tests/backend/crud ../../tests/backend/routes/test_telemetry.py ../../tests/backend/routes/test_trace_linking_timing.py ../../tests/backend/tasks
# 546 passed, 3 skipped

uv run pytest ../../tests/backend/services
# 1862 passed, 1 skipped, 1 xfailed

uv run pytest ../../tests/backend/routes ../../tests/backend/security
# 2514 passed, 39 skipped

Skips are pre-existing @pytest.mark.skips. A repo-wide grep across apps/, tests/, sdk/, ee/, packages/ and penelope/ for the seven old crud.* names returns nothing, and there is no getattr(crud, ...)/hasattr(crud, ...) reflection anywhere that could reach them dynamically.

Two pre-existing ruff findings remain in routers/test_result.py (I001, and unused typing.Optional). Both were confirmed against a stashed baseline and left alone rather than mixed into this refactor.

Worth a reviewer's eye: the two file test modules patch by module attribute, so "...results.crud" became "...results.file_crud" and mock_crud became mock_file_crud. Left unchanged these would have failed loudly on assert_called_once() rather than silently passing.

[peqy]

Looks good. Clean extraction into crud/file.py with call sites + tests updated consistently; the func import cleanup in crud/__init__.py makes sense. Ship it.