Doom-style weapon audio batch + remove footsteps

- Regenerated all 13 weapon fire one-shots and 4 weapon loops via the audio
  specialist (ElevenLabs) with a 1993 Doom style brief: chunky, bass-heavy,
  crunchy 90s FPS sounds
- New clips wired into SfxBank: ui_active, ui_active_empty (active items),
  ui_curse (legendary pickups, replaces the normal item jingle), plr_revive
  (Second Skin revive)
- Footstep system removed entirely (never worked right): Sfx.footstep, 8
  plr_step* samples and bank entries, player.js call site, smoke test block
- Cache v=42

js/items.js

@@ -176,9 +176,9 @@ function giveItem(iid) {
     spawnText(p.x, p.y - 14, 'UPGRADED!', '#ffd060');
   } else {
     addToast(item.name, item.desc);
-    spawnText(p.x, p.y - 14, item.name.toUpperCase(), '#c9a227');
+    spawnText(p.x, p.y - 14, item.name.toUpperCase(), ITEM_RARITY[item.rarity].color);
   }
-  Sfx.item();
+  if (item.rarity === 'legendary') Sfx.curse(); else Sfx.item();
   refreshOrbitals(p);
 }