revert(eink): drop full refresh on screen change — too much black-flash

A full (non-partial) refresh on every screen change (638eea7b) turned out to be
far too aggressive on real e-ink hardware: every navigation black-flashes,
which is worse than the ghosting it was clearing. Remove the whole mechanism —
DisplayDriver::forceFullRefresh() virtual, GxEPDDisplay's _force_full flag and
override, the endFrame() branch, and the setCurrScreen() call. E-ink is back to
interval-only full refreshes (Settings > Full refresh interval).

The favourites "(gone)"-tile prune that shipped in the same commit is kept.

Builds green: WioTrackerL1Eink_companion_solo_dual.

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

src/helpers/ui/DisplayDriver.h

@@ -272,7 +272,6 @@ public:
   virtual void setBrightness(uint8_t level) { }  // level 0-4 (min to max), no-op default
   virtual void setDisplayRotation(uint8_t rot) { }  // 0-3, no-op for fixed-orientation displays
   virtual void setFullRefreshInterval(uint8_t n) { }  // e-ink: do full refresh every n partial refreshes (0=never)
-  virtual void forceFullRefresh() { }  // e-ink: make the next frame a full (non-partial) refresh — clears ghosting on screen change; no-op on OLED
   virtual void endFrame() = 0;
 
 #ifdef ENABLE_SCREENSHOT

src/helpers/ui/GxEPDDisplay.cpp

@@ -275,14 +275,10 @@ void GxEPDDisplay::endFrame() {
   uint32_t crc = display_crc.finalize();
   if (crc != last_display_crc_value) {
     bool partial = true;
-    // A forced full refresh (e.g. screen change) clears inter-screen ghosting.
-    // Short-circuit so _partial_count isn't bumped on the forced pass; the block
-    // resets it either way, matching the interval-driven full refresh.
-    if (_force_full || (_full_refresh_interval > 0 && ++_partial_count >= _full_refresh_interval)) {
+    if (_full_refresh_interval > 0 && ++_partial_count >= _full_refresh_interval) {
       partial = false;
       _partial_count = 0;
     }
-    _force_full = false;
     display.display(partial);
     last_display_crc_value = crc;
   }

src/helpers/ui/GxEPDDisplay.h

@@ -64,7 +64,6 @@ class GxEPDDisplay : public DisplayDriver {
   int _text_sz = 1;
   uint8_t _full_refresh_interval = 0;
   uint8_t _partial_count = 0;
-  bool _force_full = false;   // set by forceFullRefresh(); consumed by the next endFrame()
 
   int16_t drawLemonChar(int16_t x, int16_t y, uint32_t cp, int sc);
   uint8_t lemonXAdvance(uint32_t cp, int sc);
@@ -145,6 +144,5 @@ public:
   }
   void setDisplayRotation(uint8_t rot) override;
   void setFullRefreshInterval(uint8_t n) override { _full_refresh_interval = n; _partial_count = 0; }
-  void forceFullRefresh() override { _force_full = true; }
   void endFrame() override;
 };