APS-19732: add hardened .npmrc (supply-chain audit SC-12282)

Add supply-chain hardening .npmrc with directives required by the
weekly Enigma audit (SC-12282): ignore-scripts, strict-ssl, save-exact,
engine-strict, legacy-peer-deps=false, audit-level=high.

Verified via npm ci on Node 18/20/22 (lockfile unchanged) and e2e
sample-test on Node 20. Node 16 fails engine-strict by design
(@playwright/test requires node>=18).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: karanshah-browserstack

.npmrc

@@ -0,0 +1,7 @@
+# Supply-chain hardening directives (SC-12282 / APS-19732)
+ignore-scripts=true
+strict-ssl=true
+save-exact=true
+engine-strict=true
+legacy-peer-deps=false
+audit-level=high