Add Bluetooth status icon to reader status bar

Display a Bluetooth icon in the status bar when BLE is connected. Also optimize memory management by lending the framebuffer instead of immediately tearing down BLE when heap is low, allowing BLE to remain active during rendering.

src/activities/reader/EpubReaderActivity.cpp

@@ -969,17 +969,15 @@ void EpubReaderActivity::render(RenderLock&& lock) {
     return;
   }
 
-  // Shed the BLE stack before rendering into a starved heap. Everything below —
-  // page deserialization, glyph caching, catch-up build steps — allocates through
-  // throwing paths that abort() on OOM under -fno-exceptions. Field data: with no
-  // shed, a session ground to <2.2 KB free (per-glyph SD fallbacks, no AA, 4.7 s
-  // pages) and then aborted on a tiny vector growth. Freeing BLE returns ~52 KB and
-  // restores a large contiguous block; the lifecycle restarts it behind its heap
-  // gate once the pressure passes.
+  FrameBufferBuildLoan buildLoan(renderer);
+
+  // If BLE leaves the reader below the render floor, lend the framebuffer before
+  // deserializing/loading the page instead of tearing BLE down immediately. The
+  // restore path still frees BLE if the framebuffer cannot be reallocated.
   if (BleHid.isRunning() && ESP.getFreeHeap() < RENDER_MIN_FREE_HEAP) {
-    LOG_ERR("ERS", "Render heap %u below floor %u; freeing BLE RAM", (unsigned)ESP.getFreeHeap(),
+    LOG_INF("ERS", "Render heap %u below floor %u; lending framebuffer", (unsigned)ESP.getFreeHeap(),
             (unsigned)RENDER_MIN_FREE_HEAP);
-    bleinput::stop();
+    buildLoan.release();
   }
 
   const auto showPendingSyncSaveError = [this]() {
@@ -988,8 +986,6 @@ void EpubReaderActivity::render(RenderLock&& lock) {
     GUI.drawPopup(renderer, tr(STR_SAVE_PROGRESS_FAILED));
   };
 
-  FrameBufferBuildLoan buildLoan(renderer);
-
   // A section build failure (e.g. an invalid/corrupt EPUB that fails XML parsing) leaves the
   // "Indexing" popup on screen with no way forward. Surface an explicit error instead of hanging.
   // clearScreen first so the error popup doesn't overlay the stale "Indexing" popup.
@@ -1639,7 +1635,7 @@ void EpubReaderActivity::renderStatusBar() const {
   }
 
   GUI.drawStatusBar(renderer, bookProgress, currentPage, pageCount, title, 0, textYOffset, true, currentPageBookmarked,
-                    section->isBuilding());
+                    section->isBuilding(), BleHid.isConnected());
 }
 
 void EpubReaderActivity::navigateToHref(const std::string& hrefStr, const bool savePosition) {