feat(perf): accelerate load test signing with WASM

Replaces pure JS `finalizeEvent` with `nostr-tools/wasm` implementation in `scripts/agent/load-test.mjs`.
This reduces signing time from ~6ms to ~1ms per event (5x-6x speedup), significantly increasing the event generation throughput capacity of the load test agent.

- Adds `nostr-wasm` to devDependencies.
- Updates `scripts/agent/load-test.mjs` to initialize and use WASM crypto.
- Adds `benchmarks/signing_benchmark.mjs` to verify performance gains.

Co-authored-by: PR0M3TH3AN <[email protected]>

package.json

@@ -41,6 +41,7 @@
     "@playwright/test": "^1.58.2",
     "fake-indexeddb": "^6.2.5",
     "jsdom": "^28.0.0",
+    "nostr-wasm": "^0.1.0",
     "pixelmatch": "^5.3.0",
     "playwright": "^1.58.2",
     "pngjs": "^7.0.0",