feat(fifa17): ownership-backed squad manager, not opaque round-trip

Move the squad manager from an opaque, unvalidated wire ref in the squad
extension to a resolved, ownership-backed assignment (Core migration 0023
squad_managers).

- squad::to_proposed reverse-resolves the manager wire ref to a Core
  owned_card_id on ProposedSquad; an unresolvable manager is reported as
  an unresolved wire id (a live save is refused rather than assigning a
  manager the club does not own).
- squad_ext: drop the opaque manager field from Fifa17SquadExtensionV1
  (clean cutover) and the now-unused SquadEntityRef->WireItemRef From.
- squad_projection: project the manager as the STATIC_REVERSED [{id,dream}]
  wire ref resolved from the owned assignment; absent -> [] (never faked).
  Richer manager itemData (contract/league/nation) is INFERRED-only and
  left out pending wire reversal.
- import(apply): drop a historical dangling manager ref rather than
  failing the whole import (live PUTs still refuse an unresolved manager).

openfut-import-fifa17/src/apply.rs

@@ -208,7 +208,15 @@ pub fn plan_apply(
             .and_then(|s| s.get(0))
             .context("report says a squad is present but profile has no squads[0]")?;
         let body = serde_json::to_vec(raw_squad).context("re-serialize source squad")?;
-        let put = parse_squad_put(&body).map_err(|e| anyhow::anyhow!("parse source squad: {e}"))?;
+        let mut put =
+            parse_squad_put(&body).map_err(|e| anyhow::anyhow!("parse source squad: {e}"))?;
+        // A HISTORICAL profile may reference a manager whose owned instance is
+        // not imported (unsupported/deferred, or a dangling id with no owned
+        // item at all). Drop such a manager ref here rather than failing the
+        // whole import — the manager assignment is only imported when its owned
+        // instance is. (A LIVE squad PUT still refuses an unresolved manager,
+        // because the client is actively assigning one it must own.)
+        put.manager.retain(|m| wire_to_owned.contains_key(&m.id));
         let build = build_squad_write(&put, &MapResolver(&wire_to_owned))
             .map_err(|e| anyhow::anyhow!("build squad write: {e}"))?;
         let formation = build