fix(permissions): admin can no longer operate tests — start/submit/edit/create, view only

Admin still bypassed require_any_role (non-strict) on the pure
operator actions: start-execution, submit-red, start-blue-work,
submit-blue, pause/resume-timer, and the red/blue field-edit + general
test create/update/remediation/import-rt/template endpoints all used
the loose dependency even where admin wasn't in the role tuple.
Switched every one of these to require_any_role_strict, matching the
review/validate/dispute/hold/assign endpoints already fixed earlier.

Frontend: removed every remaining role === "admin" disjunct gating
Start Execution, Submit to Blue Team, blue evaluating actions, timer
control, red/blue field editing, test creation, and template creation.
Team-blindness visibility (isBlind) deliberately keeps the admin
bypass — admin still sees both sides unmasked for oversight, since
that's visibility, not operating.

Updated ~20 tests whose fixtures used the admin account as a
convenience shortcut to create/drive tests through the workflow —
switched them to a red_lead account, fixing an incidental
fixture-resolution-order cookie bug along the way (client's cookie
jar prefers the last-logged-in role's cookie over any Bearer header
explicitly passed to a later request).

backend/tests/test_resolve_dispute_router.py

@@ -36,7 +36,7 @@ def _reach_disputed(client, db, api, auth_headers, red_tech_headers, red_lead_he
                      blue_tech_headers, blue_lead_headers, technique):
     """Drive a fresh test all the way to disputed: red approves, blue rejects."""
     resp = api(
-        "post", "/api/v1/tests", auth_headers,
+        "post", "/api/v1/tests", red_lead_headers,
         json={"technique_id": technique, "name": "Dispute test"},
     )
     test_id = resp.json()["id"]