fix(ui): trim verbose startup notice; show daemon output on shutdown for external daemons

- Loading "taking longer than expected" notice: shorten the body + hint so the
  startup screen reads less wordy (same info, ~half the text).
- Shutdown screen: when the wallet attached to an EXTERNAL daemon (no captured
  stdout — debug_log_path_ is only set when we spawn it), the "dragonxd output"
  panel was always empty, leaving just a spinner. Fall back to tailing the
  daemon's debug.log so the user can watch the node flush the block index and
  exit. Adds App::tailDaemonDebugLog() (best-effort, reads only the file tail).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app.h

@@ -175,6 +175,13 @@ public:
      */
     void renderShutdownScreen();
 
+    /**
+     * @brief Tail the last N lines of the daemon's debug.log (best-effort, reads only the file tail).
+     * Fallback for the shutdown screen when we have no captured stdout — e.g. an external daemon we
+     * attached to rather than spawned — so the user can still see the node flushing/exiting.
+     */
+    std::vector<std::string> tailDaemonDebugLog(int maxLines) const;
+
     /**
      * @brief Render loading overlay in content area while daemon is starting/syncing
      * @param contentH Height of the content area child window