test(backend): integration marker + conftest gating for the real-DB lane

[AndresL230]

Context

tests/conftest.py has two autouse fixtures that make the default suite hermetic: _hermetic_supabase_client (:47-77) and _bypass_session_auth (:80-143), both currently exempting only the e2e_staging marker. Open PR #377 already implements this issue — it registers an integration marker and extends both fixtures to bypass under it (real DB client + real auth guard). This issue exists to land and verify that work as part of the epic; if #377 merges first, close this on arrival. Supersedes #362, which is closed in favor of this epic's granular issues.

Scope

• Register the integration marker; both autouse fixtures skip under it so the lane gets a real client and a real minted session.
• Do not fork conftest.
• Delta-check against PR Local-Supabase follow-ups: rich seed + integration suite (#363, #362; #365 reverted) #377 rather than reimplementing.

Acceptance criteria

• pytest -m integration gets a real DB client and a real minted session.
• Default hermetic suite (970 tests) unaffected.

Dependencies

Depends on: #378
Blocks: #397

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Chapter: 1 (Regression Suite) | Lane: subcutaneous | Size: S | Suggested owner: Luke
Part of epic #402

[AndresL230]

Closing as already delivered — verified against main at 5dee71d.

This issue's own text anticipated it: "if #377 merges first, close this on arrival." PR #377 merged (a97fa61), and PR #411 (#379) extended the same pattern to a third guard.

Every scope item is on main:

• integration marker registered — backend/tests/conftest.py:35, in pytest_configure.
• Autouse hermetic fixtures bypass under it — _hermetic_supabase_client (:68) and _bypass_session_auth (:99) both early-return on request.node.get_closest_marker("integration"), so the lane gets a real db.connection._client and the real auth_guard.
• A third guard now exists and also exempts it — _hermetic_llm_transport, added by test(backend): hermetic LLM guard fixture — fail on unstubbed Gemini egress #379 after this issue was written, exempts e2e_staging / integration / live_llm.
• conftest was not forked — all of it lives in the single root tests/conftest.py.

Acceptance criteria:

• pytest -m integration gets a real DB client and a real minted session — exercised today by backend/tests/integration/test_local_stack.py.
• Default hermetic suite unaffected — 1034 passing at 5dee71d (the "970" in the original text is now 1034 after test(backend): hermetic LLM guard fixture — fail on unstubbed Gemini egress #379/test(backend): cookie-minting test-auth endpoint for local/test envs #381 added tests).

No delta work remains. The real gap this lane still has is #397 (raw-SQL assertions, truncate isolation, user factories), which has been re-scoped against current main.