fix(l2): map download no longer stalls on busy tile servers

A 404/503 answer (OpenTopoMap renders on demand) went to an immediate
2 s retry and counted as network loss, so each tile then waited up to
60 s. Answered errors now go straight to the retry list; long pauses
only when there is no answer at all. Three retry rounds (20/60/120 s)
for the tiles still missing, transfers cut after 30 s, failures logged
on serial.

Download popup tidied: title + floating close, percentage instead of
tile counts (also on the map pill), no dead zoom row, no finish toast
after Stop or while the popup shows the result.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-lvgl/UITask.h

@@ -102,7 +102,6 @@ public:
   void mapDownloadStop();
   void mapDownloadResume();
   void mapDownloadDiscard();
-  void mapDownloadZmax(int delta);
   void setLiveTiles(bool on);
   void setTrails(bool on);
   void setVectorMap(bool on);
@@ -567,11 +566,10 @@ private:
   lv_obj_t* _dl_info = nullptr;
   lv_obj_t* _dl_bar = nullptr;          // progress while downloading
   lv_obj_t* _dl_err = nullptr;          // failures, one line
-  lv_obj_t* _dl_zoom_lbl = nullptr;
+  lv_obj_t* _dl_sub = nullptr;
   lv_obj_t* _dl_start_lbl = nullptr;
   lv_obj_t* _dl_job_row = nullptr;      // "Unfinished ... Resume" in the popup
   lv_obj_t* _dl_job_lbl = nullptr;
-  int       _dl_zmax = 0;
   uint8_t   _dl_last_state = 0;
 
   // Navigation map (SCR_MAP with _map_nav)