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>

lib/EpdFont/EpdFontFamily.h

@@ -10,7 +10,6 @@ class EpdFontFamily {
       : regular(regular), bold(bold), italic(italic), boldItalic(boldItalic) {}
   ~EpdFontFamily() = default;
   void getTextDimensions(const char* string, int* w, int* h, Style style = REGULAR) const;
-  bool hasPrintableChars(const char* string, Style style = REGULAR) const;
   const EpdFontData* getData(Style style = REGULAR) const;
   const EpdGlyph* getGlyph(uint32_t cp, Style style = REGULAR) const;