feat(core): one instance-based ownership model for every kind of owned content

Core could only own players. Everything else a FUT club holds — managers, staff,
consumables, kits, badges, balls, stadiums — had no representation, so the only
way to show one to a client was to synthesise it on read. That is the failure
mode this commit exists to make impossible: read authority, write authority and
persistent ownership authority are now the same rows.

MODEL. There is deliberately NO parallel items table. A manager, a consumable, a
kit and a player are all rows in `owned_cards`, differing only by a new
game-INDEPENDENT `content_kind` (player|manager|staff|consumable|kit|badge|ball|
stadium|misc). A game adapter translates its own taxonomy — FIFA 17's
`cardsubtypeid` and resource ranges — into one of those tokens before ownership
reaches Core; no game's numerics land here. Ownership stays INSTANCE-based:
`card_id` is the definition, `id` is the instance, and two copies of one
definition remain two rows.

`quantity` is a nullable per-instance attribute, not a replacement for the
instance. The real profile settles this: its 17 consumables are instance-based
and only SOME carry a wire `amount` (observed 1,2,4,5,10,15), while two copies of
definition 5003068 exist as two distinct instances. So NULL means "not a stack"
and a positive integer is the stack size; collapsing instances into counts is
forbidden by the model.

ACTIVE DESIGNATIONS. Migration 0024's two-slot kit table becomes
`club_active_items` over the five slots that correspond exactly to the client's
recovered equipped-state vocabulary (activeBadge 100, activeHomeKit 101,
activeAwayKit 102, activeBall 103, activeStadium 104). There is no
activeLeagueLogo or activeMisc token, so those kinds correctly get no slot. The
invariants are schema-enforced rather than conventional: PK(club_id, slot) allows
at most one item per role, `owned_card_id UNIQUE` makes "the same card is both
home and away kit" unstorable, and ON DELETE CASCADE means a quick-sold or
consumed item cannot be projected back as active. 0024's trigger is preserved in
semantics — and dropped EXPLICITLY before its table, because it lives ON
`owned_cards`, so DROP TABLE would have orphaned it and broken every later
ownership transfer. It still exists because the market moves ownership by UPDATE,
which no foreign key can observe.

CONSUMABLE ACTIONS. `services/consume.rs` is one transaction primitive —
validate source ownership and kind, validate target, mutate, consume the source
exactly once, commit — guarded by `UNIQUE(profile_id, action_identity)` in
migration 0027, the same discipline as `match_completions`. It supports both
deleting the row and decrementing a stack, chosen by the caller, inside the one
transaction and the one replay guard. It deliberately contains NO category
formulas: an unreversed effect must not be invented, so callers supply the
mutation and category validation stays explicit.

`/club/kits` is replaced by slot-generic `/club/active-items`. `get_collection`
now carries `content_kind` and `quantity`, accepts a `content_kind` filter, and
— importantly — stops dropping an owned card with a missing definition silently:
the envelope reports `owned_rows`, `unresolved_items` and the offending
definition ids. That silent `filter_map` is the documented cause of a club that
looks empty while the rows are all present.

Verified against a REAL populated club, not a fixture: the production snapshot
(migration 19) is copied to a tempdir, migrated to 0024, given two kit
designations on real owned instances, then migrated to head. 1986 owned rows
survive as content_kind='player', both designations land in `club_active_items`,
no row gains a quantity, and the old table is gone. 258 tests pass, clippy clean.

tests/import_service_test.rs

@@ -2,6 +2,7 @@
 //! the Core-level half of the migration mutation battery: each hostile input is
 //! rejected BEFORE any partial write, and re-runs converge instead of duplicating.
 
+use openfut_core::models::card::ContentKind;
 use openfut_core::services::card_db::CardDb;
 use openfut_core::services::import::{
     apply_profile_import, ImportClub, ImportEntitlement, ImportExtension, ImportOwnedCard,
@@ -34,6 +35,8 @@ fn owned(ids: &[String]) -> Vec<ImportOwnedCard> {
         .map(|(i, id)| ImportOwnedCard {
             owned_item_id: format!("oc-{i}"),
             card_id: id.clone(),
+            content_kind: ContentKind::Player,
+            quantity: None,
         })
         .collect()
 }
@@ -208,6 +211,8 @@ async fn missing_definition_fails_preflight_with_no_writes() {
     ow.push(ImportOwnedCard {
         owned_item_id: "oc-bad".into(),
         card_id: "fifa17_definitely_absent_999999".into(),
+        content_kind: ContentKind::Player,
+        quantity: None,
     });
     let err = apply_profile_import(&pool, &db, &request("g_miss", "fp", ow, None))
         .await