fix(1.0.5): revert Sec-CH-UA spoof (white pages), add DevTools shortcut

- Sec-CH-UA / Sec-CH-UA-Mobile / Sec-CH-UA-Platform header overrides on
  every request in 1.0.4 broke page rendering (all views white). Reverted
  to image-Referer-only behavior from 1.0.3. The Google "embedded browser"
  fix in 1.0.4 came primarily from the adblock whitelist (which IS kept)
  — Sec-CH-UA spoofing was the suspect for the regression.
- Ctrl+Shift+I and F12 now open DevTools on the main shell and on every
  in-app browser view. Always-on so kiosk machines can be debugged
  without leaving kiosk mode.
- Restore session sequenced (await 150ms between tabs) to avoid concurrent
  create-view races where multiple setLoader/addChild interleaved.
- Update banner now shows error state with a "Повторить" button instead
  of hiding it, so install-update failures are visible to the user.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/styles/main.css

@@ -1480,6 +1480,11 @@ body {
 }
 .update-banner-close:hover { color: #fff; }
 
+.update-banner.error {
+  border-color: rgba(229,9,20,0.5);
+  background: rgba(40,10,12,0.95);
+}
+
 .update-banner-progress {
   flex: 1;
   height: 4px;