test(fifa17): smoke-test the apply probe and prove the gate fails closed

Unit tests cover classification and body parsing; they do not prove the running
host behaves. These three scripts exercise the real service, and they found
nothing broken but make the two load-bearing claims checkable:

fifa17-apply-snapshot.py   Core truth around an apply: coins, owned rows, kind
                           histogram, the source stack's copy count, and the
                           target's mutable fields (contract/fitness/playStyle/
                           training/injury). Coins and ownership come from the
                           staging DB, not the wire, so the check cannot be
                           satisfied by a projection bug.

fifa17-apply-probe-smoke.py  Replays the EXACT captured request plus the edges,
                           against the live host, no client needed:
                             1. {"apply":[{"id":100000003}]} -> 200 {"itemData":[]}
                                source=Consumable subtype=201 copies=1,
                                target=fifa17_200389 rating=87
                             2. two targets            -> 400 apply_batch_unsupported
                             3. unknown target wire id -> 200 UNRESOLVED_WIRE_ID
                             4. unowned source         -> 200 NOT_OWNED
                           then re-snapshots: Core identical after all four.

fifa17-apply-gate-off.py   The production-safety claim. With APPLY_PROBE unset
                           the same request must produce the pre-probe
                           behaviour, and does: no apply-probe line, three
                           passthrough lines, 502 into the dead upstream, Core
                           unchanged. Verified by restarting staging without the
                           flag -- an assertion about failing closed is worth
                           nothing unless the closed path is executed.

Nothing here writes to production; snapshot reads the staging DB read-only.

scripts/fifa17-apply-gate-off.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python3
+"""With OPENFUT_FIFA17_APPLY_PROBE unset the apply MUST fall through to the
+Python passthrough -- i.e. exactly the behaviour that existed before the probe.
+That is the production-safety claim, so prove it rather than assert it."""
+import subprocess
+import urllib.error
+import urllib.request
+
+LOG = "/home/alex/openfut-sold-staging/logs/utas-host.log"
+mark = sum(1 for _ in open(LOG))
+before = subprocess.run(["python3", "/home/alex/OpenFUT/scripts/fifa17-apply-snapshot.py"],
+                        capture_output=True, text=True).stdout
+
+req = urllib.request.Request(
+    "http://127.0.0.1:8299/ut/game/fifa17/item/resource/5001004",
+    data=b'{"apply":[{"id":100000003}]}',
+    headers={"X-OpenFUT-Game": "fifa17", "Content-Type": "application/json"},
+    method="POST")
+try:
+    with urllib.request.urlopen(req, timeout=30) as r:
+        st, body = r.status, r.read().decode()
+except urllib.error.HTTPError as e:
+    st, body = e.code, e.read().decode()
+print("  status=%s body=%s" % (st, body))
+
+print("--- log with the gate OFF ---")
+lines = list(open(LOG))[mark:]
+for line in lines:
+    if any(k in line for k in ("apply-probe", "passthrough", "PYTHON")):
+        print("   " + line.rstrip()[:150])
+
+probe_served = any("apply-probe" in line for line in lines)
+went_python = any("owner=PYTHON" in line for line in lines)
+after = subprocess.run(["python3", "/home/alex/OpenFUT/scripts/fifa17-apply-snapshot.py"],
+                       capture_output=True, text=True).stdout
+print("\n  probe served (must be False): %s" % probe_served)
+print("  proxied to Python (must be True): %s" % went_python)
+print("  Core unchanged: %s" % (before == after))
+print("\nRESULT: %s" % ("OK -- gate fails closed"
+                        if (not probe_served and went_python and before == after)
+                        else "FAILED"))