fix(fifa17): route the client's lowercase usermassinfo to the Rust handler

The retail client sends BOTH casings. Observed twice on staging, each time
inside a genuine client sequence:

  16:56:56  route=squad-active 200
  16:56:56  GET /ut/game/fifa17/usermassinfo -> passthrough -> 502
  16:56:56  route=userMassInfo 200

classify matched the exact literal `userMassInfo`, so the lowercase request
fell through to the Python upstream. Today that is a harmless 502 because the
upstream is dead and the client immediately retries with the canonical casing -
but on a deployment with Python ALIVE that request would be ANSWERED there,
silently splitting authority away from Rust for a route Core owns. That is the
real defect, not the wasted round trip.

Fixed with the smallest possible alias: this one tail is matched
case-insensitively, the rest of the table stays exact since no other route has
ever shown a casing variant. Paths are NOT globally lowercased.

Tests cover the canonical casing, lowercase, uppercase, two adjacent tails that
must NOT be swept up by the alias (`usermassinfox`, `usermass`), and method
semantics (PUT/POST still passthrough). With the alias reverted the test fails.

openfut-utas-host/tests/host_test.rs

@@ -1079,6 +1079,38 @@ fn classify_squad_and_usermassinfo_routes() {
         classify("GET", "/ut/game/fifa17/userMassInfo"),
         Route::UserMassInfo
     );
+    // The retail client sends the lowercase tail too, immediately before the
+    // canonical one. It must reach the SAME Rust-owned handler: falling through
+    // to Python is a 502 here and, with Python alive, an authority split.
+    assert_eq!(
+        classify("GET", "/ut/game/fifa17/usermassinfo"),
+        Route::UserMassInfo,
+        "lowercase usermassinfo is a real retail request, observed twice"
+    );
+    assert_eq!(
+        classify("GET", "/ut/game/fifa17/USERMASSINFO"),
+        Route::UserMassInfo
+    );
+    // Adjacent tails must NOT be swept up by the case-insensitive arm.
+    assert_eq!(
+        classify("GET", "/ut/game/fifa17/usermassinfox"),
+        Route::Passthrough,
+        "the alias must match the whole tail, not a prefix"
+    );
+    assert_eq!(
+        classify("GET", "/ut/game/fifa17/usermass"),
+        Route::Passthrough
+    );
+    // Method semantics are unchanged: only GET is this route.
+    assert_eq!(
+        classify("PUT", "/ut/game/fifa17/usermassinfo"),
+        Route::Passthrough
+    );
+    assert_eq!(
+        classify("POST", "/ut/game/fifa17/userMassInfo"),
+        Route::Passthrough
+    );
+
     // GET /squad/active and every numeric GET are the one Core-backed current
     // squad, matching the oracle's single-squad response regardless of URL id.
     assert_eq!(