## Summary
* **What is the goal of this PR?**
Improve reliability and user experience during chapter indexing by
adding retry logic for SD card operations and a visual progress bar.
* **What changes are included?**
- **Retry logic**: Add 3 retry attempts with 50ms delay for ZIP to SD
card streaming to handle timing issues after display refresh
- **Progress bar**: Display a visual progress bar (0-100%) during
chapter indexing based on file read progress, updating every 10% to
balance responsiveness with e-ink display limitations
## Additional Context
* **Problem observed**: When navigating quickly through books with many
chapters (before chapter titles finish rendering), the "Indexing..."
screen would appear frozen. Checking the serial log revealed the
operation had silently failed, but the UI showed no indication of this.
Users would likely assume the device had crashed. Pressing the next
button again would resume operation, but this behavior was confusing and
unexpected.
* **Solution**:
- Retry logic handles transient SD card timing failures automatically,
so users don't need to manually retry
- Progress bar provides visual feedback so users know indexing is
actively working (not frozen)
* **Why timing issues occur**: After display refresh operations, there
can be timing conflicts when immediately starting SD card write
operations. This is more likely to happen when rapidly navigating
through chapters.
* **Progress bar design**: Updates every 10% to avoid excessive e-ink
refreshes while still providing meaningful feedback during long indexing
operations (especially for large chapters with CJK characters).
* **Performance**: Minimal overhead - progress calculation is simple
byte counting, and display updates use `FAST_REFRESH` mode.
* white sleep screen
* quicker pwr button
* no extra spacing between paragraphs
* Added settings class with de/serialization and whiteSleepScreen setting to control inverting the sleep screen
* Added Settings screen for real, made settings a global singleton
* Added setting for extra paragraph spacing.
* fixed typo
* Rework after feedback
* Fixed type from bool to uint8
* First pass at moving to SDK EInkDisplay library
* Add 2-bit grayscale text and anti-aliased rendering of text
* Render status bar for empty chapters
* Refresh screen every 15 pages to avoid ghosting
* Simplify boot and sleep screens
* Give FileSelectionScreen task more stack memory
* Move text around slightly on Boot and Sleep screens
* Re-use existing buffer and write to whole screen for 'partial update'
