feat: m4 teil 1 — beute, inventar und affixe

- data/: [[loot_tables]] und [[affixes]] als Registries; LootEntry mit
  guaranteed, nothing, table-in-table, count und affixes
- game/loot.rs: EINE Ziehmaschinerie fuer Gegenstaende und Affixe,
  Tiefendeckel gegen wechselseitigen Bezug
- PickUp zieht erst beim Aufheben (Ticket 16) — moeglich nur, weil alle
  Haufen dasselbe Symbol zeigen
- UseItem/Equip/Unequip/Drop, Inventar-Screen als Registry-Schleife
- Affixe im Attributpfad, in der Resistenz und in der Trigger-Suche;
  item_label stellt Affixnamen voran, item_price multipliziert Faktoren
- Room haelt eine loot_table (nicht je Haufen eine), Prefab-loot
  ueberschreibt die Etagentabelle

53 Tests. Offen aus M4: Handel.

mods/core/floors.toml

@@ -16,6 +16,7 @@ rooms    = 7
 required = ["core:entrance", "core:stairs", "core:merchant"]
 prefabs  = [ { tag = "core:normal", weight = 10 } ]
 creatures = [ { id = "core:rat", weight = 10 } ]
+loot      = "core:floor_1_table"
 
 [[floors]]
 id       = "floor_2"
@@ -26,6 +27,7 @@ required = ["core:entrance", "core:stairs", "core:merchant"]
 prefabs  = [ { tag = "core:normal", weight = 10 },
              { tag = "core:treasure", weight = 2 } ]
 creatures = [ { id = "core:rat", weight = 6 }, { id = "core:skeleton", weight = 6 } ]
+loot      = "core:floor_1_table"
 
 [[floors]]
 id       = "floor_3"
@@ -36,6 +38,7 @@ required = ["core:entrance", "core:stairs", "core:merchant"]
 prefabs  = [ { tag = "core:normal", weight = 10 },
              { tag = "core:treasure", weight = 3 } ]
 creatures = [ { id = "core:rat", weight = 3 }, { id = "core:skeleton", weight = 8 }, { id = "core:ghoul", weight = 3 } ]
+loot      = "core:floor_3_table"
 
 [[floors]]
 id       = "floor_4"
@@ -46,6 +49,7 @@ required = ["core:entrance", "core:stairs", "core:merchant"]
 prefabs  = [ { tag = "core:normal", weight = 10 },
              { tag = "core:treasure", weight = 3 } ]
 creatures = [ { id = "core:skeleton", weight = 6 }, { id = "core:ghoul", weight = 8 } ]
+loot      = "core:floor_3_table"
 
 [[floors]]
 id       = "floor_5"
@@ -56,3 +60,4 @@ required = ["core:entrance", "core:stairs", "core:merchant"]
 prefabs  = [ { tag = "core:normal", weight = 10 },
              { tag = "core:treasure", weight = 4 } ]
 creatures = [ { id = "core:ghoul", weight = 8 }, { id = "core:bone_lord", weight = 2 } ]
+loot      = "core:floor_5_table"