feat: port upstream PRs #852, #965, #972, #971, #977, #975

Port 6 upstream PRs (PR #939 was already ported):

- #852: Complete HalPowerManager with RAII Lock class, WiFi check in
  setPowerSaving, skipLoopDelay overrides for ClearCache/OtaUpdate,
  and power lock in Activity render task loops
- #965: Fix paragraph formatting inside list items by tracking
  listItemUntilDepth to prevent unwanted line breaks
- #972: Micro-optimizations: std::move in insertFont, const ref for
  getDataFromBook parameter
- #971: Remove redundant hasPrintableChars pre-rendering pass from
  EpdFont, EpdFontFamily, and GfxRenderer
- #977: Skip unsupported image formats before extraction, add
  PARSE_BUFFER_SIZE constant and chapter parse timing
- #975: Fix UITheme memory leak by replacing raw pointer with
  std::unique_ptr for currentTheme

Co-authored-by: Cursor <cursoragent@cursor.com>

src/activities/Activity.cpp

@@ -1,5 +1,7 @@
 #include "Activity.h"
 
+#include <HalPowerManager.h>
+
 void Activity::renderTaskTrampoline(void* param) {
   auto* self = static_cast<Activity*>(param);
   self->renderTaskLoop();
@@ -9,6 +11,7 @@ void Activity::renderTaskLoop() {
   while (true) {
     ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
     {
+      HalPowerManager::Lock powerLock;
       RenderLock lock(*this);
       render(std::move(lock));
     }

src/activities/ActivityWithSubactivity.cpp

@@ -1,9 +1,12 @@
 #include "ActivityWithSubactivity.h"
 
+#include <HalPowerManager.h>
+
 void ActivityWithSubactivity::renderTaskLoop() {
   while (true) {
     ulTaskNotifyTake(pdTRUE, portMAX_DELAY);
     {
+      HalPowerManager::Lock powerLock;
       RenderLock lock(*this);
       if (!subActivity) {
         render(std::move(lock));

src/activities/settings/ClearCacheActivity.h

@@ -14,6 +14,7 @@ class ClearCacheActivity final : public ActivityWithSubactivity {
   void onExit() override;
   void loop() override;
   void render(Activity::RenderLock&&) override;
+  bool skipLoopDelay() override { return true; }
 
  private:
   enum State { WARNING, CLEARING, SUCCESS, FAILED };

src/activities/settings/OtaUpdateActivity.h

@@ -33,5 +33,6 @@ class OtaUpdateActivity : public ActivityWithSubactivity {
   void onExit() override;
   void loop() override;
   void render(Activity::RenderLock&&) override;
+  bool skipLoopDelay() override { return true; }
   bool preventAutoSleep() override { return state == CHECKING_FOR_UPDATE || state == UPDATE_IN_PROGRESS; }
 };