ci(security): Faz 3 + ekstra — runner consolidation, auto-rollback, cosign, SRI, dep cleanup

* Faz 3.1 — All CI jobs moved to self-hosted pwap-runner (DEV VPS).
  No more dependency on GitHub-hosted runners — supply-chain attack
  surface from GHA runner image compromise eliminated.
* Faz 3.3 — Automatic rollback on health-check fail. Each deploy stamps
  /.deploy-sha into the artifact. On health-check failure, the deploy
  job reads the previous SHA from the live site, pulls that image, and
  redeploys. Telegram notification differentiates: rolled-back-OK,
  rollback-also-failed, no-prev-available, manual-rollback-needed.
* E.3 — cosign keyless image signing. build-image signs the GHCR
  manifest via Sigstore Fulcio (OIDC, no long-lived keys). deploy-app
  and deploy-pex verify the signature before extracting /dist —
  unsigned or tampered images cannot deploy. Identity-pinned to this
  workflow file.
* E.5 — Subresource Integrity (SRI). vite-plugin-subresource-integrity
  injects sha384 integrity= into <script>/<link> tags at build time.
  CDN/proxy compromise cannot inject tampered JS — browser blocks on
  hash mismatch.
* E.2 — Dependabot triage. 14 alerts: 7 high + 4 moderate cleared via
  npm audit fix + npm overrides (elliptic, create-ecdh). 6 low
  (transitive in vite-plugin-node-polyfills chain) accepted; the
  upstream fix proposes a semver-major DOWNGRADE which makes no sense.
* E.1 — Branch protection on main: CI Gate ✅ required, 1 review
  required, force-push and deletion blocked.

web/package.json

@@ -120,7 +120,9 @@
     "@pezkuwi/x-textdecoder": "^14.0.25",
     "@pezkuwi/x-textencoder": "^14.0.25",
     "@pezkuwi/x-ws": "^14.0.25",
-    "@pezkuwi/networks": "^14.0.25"
+    "@pezkuwi/networks": "^14.0.25",
+    "elliptic": "^6.6.1",
+    "create-ecdh": "^5.0.1"
   },
   "devDependencies": {
     "@eslint/js": "^9.9.0",
@@ -147,6 +149,7 @@
     "typescript-eslint": "^8.0.1",
     "vite": "^7.3.1",
     "vite-plugin-node-polyfills": "^0.25.0",
+    "vite-plugin-subresource-integrity": "^0.0.12",
     "vitest": "^4.0.10"
   }
 }