fix: resolve intermittent auth errors when navigating between tabs

Token refresh race condition: when multiple requests got 401 simultaneously,
queued retries reused stale headers and the initiator fell through without
throwing on retry failure. Now retries regenerate headers (fresh request ID
and CSRF token), and both retry failure and refresh failure throw explicitly.

SWR cache is now invalidated after token refresh so stale error responses
are not served from cache.

CHANGELOG.md

@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 ### Fixed
 
+- **No more random errors when switching tabs.** Navigating between Dashboard, Funnels, Uptime, and Settings no longer shows "Invalid credentials", "Something went wrong", or "Site not found" errors. This was caused by a timing issue when your login session refreshed in the background while multiple pages were loading at the same time — all those requests now wait for the refresh to finish and retry cleanly.
 - **More accurate pageview counts.** Refreshing a page no longer inflates your pageview numbers. The tracking script now detects when the same page is loaded again within a few seconds and skips the duplicate, so metrics like total pageviews, pages per session, and visit duration reflect real navigation instead of reload habits.
 - **Self-referrals no longer pollute your traffic sources.** Internal navigation within your own site (e.g. clicking from your homepage to your about page) no longer shows your own domain as a referrer. Only external traffic sources appear in your Referrers panel now.
 - **Screen size fallback now works correctly.** A variable naming issue prevented the fallback screen dimensions from being read when the primary value wasn't available. Screen size data is now reliably captured on all browsers.