feat(lite): Console tab with connection + open/create diagnostics

The lite variant had no visibility into why a wallet failed to open — just a
"disconnected" spinner. Add a lite-only Console tab (full-node keeps its RPC
console) that shows a live diagnostic log.

- LiteDiagnostics: a small thread-safe, bounded ring buffer (header-only). The
  controller writes to it from its background threads: each failover server
  attempt and result, wallet open/create/restore outcomes, sync start, and
  blocked-open reasons. The App logs controller (re)builds with the preferred
  server.
- lite_console_tab: a terminal-styled, read-only view of the log (newest at the
  bottom, error/success lines coloured) with Clear / Copy / Auto-scroll. Reachable
  even when the wallet is locked (it's diagnostics, no secrets). Registered as
  NavPage::LiteConsole, gated lite-only via WalletUiSurface::LiteConsole.

A unit test drives an open-with-failover and asserts the log records the
connection attempt and the successful open. Built clean for full-node, lite, and
Windows cross-compile.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/util/i18n.cpp

@@ -1107,6 +1107,12 @@ void I18n::loadBuiltinEnglish()
         strings_["xmrig_unknown_error"]      = "Unknown error.";
 
         // --- Lite Network tab (server browser) ---
+        strings_["lite_console_title"]      = "Console";
+        strings_["lite_console_intro"]      = "Diagnostic log: server connections, wallet open/create, and sync events.";
+        strings_["lite_console_clear"]      = "Clear";
+        strings_["lite_console_copy"]       = "Copy";
+        strings_["lite_console_autoscroll"] = "Auto-scroll";
+        strings_["lite_console_empty"]      = "No diagnostic output yet.";
         strings_["lite_net_title"]        = "Lite Servers";
         strings_["lite_net_intro"]        = "Pick a server to use, or let the wallet choose one at random. Changes apply immediately.";
         strings_["lite_net_use_random"]   = "Use a random server each time";