fix(auth): survive ERR_ABORTED in login retry — recreate context, 5 attempts with backoff

- Introduce safeClose() helper that ignores 'Target page, context or
  browser has been closed' errors. When Hostinger LiteSpeed aborts a
  connection (net::ERR_ABORTED), Playwright internally marks the context
  as closed; the previous bare context.close() threw from inside catch,
  propagating out and killing setup before remaining retries ran.
- MAX_ATTEMPTS 3 → 5 for more tolerance of burst throttle windows.
- Backoff changed from flat 15 s → exponential 5/10/20/40 s (75 s total).
- Worst-case timing: 5 × 90 s nav + 75 s backoff = ~525 s < 900 s job limit.
- Final-failure message explicitly names the LiteSpeed throttle hypothesis.
- Version bump 1.2.0 → 1.3.0.

Agent-Session: engineer-e2e-authfix-20260612

package.json

@@ -1,6 +1,6 @@
 {
   "name": "peptide-e2e",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "description": "Playwright smoke tests for peptiderepo.com (staging + production)",
   "private": true,
   "scripts": {