feat: export wasm background files for direct import

Add ./dist/browser/js/wasm/wasm_utxo_bg.js and wasm_utxo_bg.wasm
to the exports field to allow webpack shims to import internal wasm
modules directly. This resolves "Package path is not exported" errors
when consuming this package in Next.js applications.

Also adds node variants for consistency.

Ticket: BTC-0

Author: lcovar

packages/wasm-utxo/package.json

@@ -48,7 +48,11 @@
       "types": "./dist/node/js/utxolibCompat.d.ts",
       "browser": "./dist/browser/js/utxolibCompat.js",
       "default": "./dist/node/js/utxolibCompat.js"
-    }
+    },
+    "./dist/browser/js/wasm/wasm_utxo_bg.js": "./dist/browser/js/wasm/wasm_utxo_bg.js",
+    "./dist/browser/js/wasm/wasm_utxo_bg.wasm": "./dist/browser/js/wasm/wasm_utxo_bg.wasm",
+    "./dist/node/js/wasm/wasm_utxo_bg.js": "./dist/node/js/wasm/wasm_utxo_bg.js",
+    "./dist/node/js/wasm/wasm_utxo_bg.wasm": "./dist/node/js/wasm/wasm_utxo_bg.wasm"
   },
   "sideEffects": [
     "./dist/node/js/wasm/wasm_utxo.js",