feat: add SD card font support with on-device download and web management

Add a complete SD card font subsystem that enables users to install and
use custom fonts beyond the three built-in families. This combines the
back-end firmware support (#1327) with the font configuration, build
pipeline, CI distribution, and user-facing management UI (#1392).

Core font system:
- Custom .cpfont binary format (v4) with multi-style support (regular,
  bold, italic, bold-italic) packed into a single file per size
- On-demand glyph loading from SD card with two-pass prewarm rendering
  to bulk-read glyphs per page, achieving near-flash performance for
  Latin text (~697ms vs ~681ms) and viable CJK rendering (~32% slower)
- Persistent advance cache for layout measurement without SD I/O
- Overflow ring buffer for glyph cache misses during rendering
- Memory-conscious design: only advance tables kept in RAM; glyph
  bitmaps, kern tables, and ligatures loaded on demand from SD

Font management:
- On-device WiFi download from GitHub Releases with manifest-based
  discovery, install/update detection, and progress UI
- Web interface font upload, listing, and deletion via /fonts page
- Manual SD card copy to /fonts/ or /.fonts/ directories
- Font selection integrated into Settings > Reader > Font Family

Build pipeline:
- Declarative YAML config (sd-fonts.yaml) as single source of truth
  for the 17-family font library (serif, sans, mono, accessibility)
- Python converter (fontconvert_sdcard.py) for TTF/OTF to .cpfont with
  FreeType rasterization, class-based kerning, and ligature extraction
- Parallel build orchestrator with variable font instance extraction
- CI workflow publishing versioned + stable releases to a dedicated
  crosspoint-fonts repository with auto-incrementing revision tags
- Centralized version constants (cpfont_version.py) shared across
  build tooling and CI, with firmware headers as manual sync points

Additional fixes:
- CJK characters no longer get hyphens inserted at line breaks
- Advance table eliminates 30+ second stalls during CJK section
  indexing for paragraphs with >512 unique codepoints

Closes #930

Co-authored-by: Zach Nelson <zach@zdnelson.com>
Co-authored-by: Justin <itsthisjustin@users.noreply.github.com>
Co-authored-by: jpirnay <jens@pirnay.com>
Co-authored-by: mcrosson <kemonine@kemonine.info>

src/components/themes/BaseTheme.cpp

@@ -231,7 +231,8 @@ void BaseTheme::drawList(const GfxRenderer& renderer, Rect rect, int itemCount,
                          const std::function<std::string(int index)>& rowTitle,
                          const std::function<std::string(int index)>& rowSubtitle,
                          const std::function<UIIcon(int index)>& rowIcon,
-                         const std::function<std::string(int index)>& rowValue, bool highlightValue) const {
+                         const std::function<std::string(int index)>& rowValue, bool highlightValue,
+                         const std::function<bool(int index)>& rowDimmed) const {
   int rowHeight =
       (rowSubtitle != nullptr) ? BaseMetrics::values.listWithSubtitleRowHeight : BaseMetrics::values.listRowHeight;
   int pageItems = rect.height / rowHeight;
@@ -279,6 +280,16 @@ void BaseTheme::drawList(const GfxRenderer& renderer, Rect rect, int itemCount,
     auto item = renderer.truncatedText(font, itemName.c_str(), textWidth);
     renderer.drawText(font, rect.x + BaseMetrics::values.contentSidePadding, itemY, item.c_str(), i != selectedIndex);
 
+    // Apply checkerboard dither to create gray text effect for dimmed items
+    if (rowDimmed && rowDimmed(i) && i != selectedIndex) {
+      const int titleWidth = renderer.getTextWidth(font, item.c_str());
+      const int lineH = renderer.getLineHeight(font);
+      const int tx = rect.x + BaseMetrics::values.contentSidePadding;
+      for (int py = itemY; py < itemY + lineH; py++)
+        for (int px = tx; px < tx + titleWidth; px++)
+          if ((px + py) % 2 == 0) renderer.drawPixel(px, py, false);
+    }
+
     if (rowSubtitle != nullptr) {
       // Draw subtitle
       std::string subtitleText = rowSubtitle(i);

src/components/themes/BaseTheme.h

@@ -138,8 +138,8 @@ class BaseTheme {
                         const std::function<std::string(int index)>& rowTitle,
                         const std::function<std::string(int index)>& rowSubtitle = nullptr,
                         const std::function<UIIcon(int index)>& rowIcon = nullptr,
-                        const std::function<std::string(int index)>& rowValue = nullptr,
-                        bool highlightValue = false) const;
+                        const std::function<std::string(int index)>& rowValue = nullptr, bool highlightValue = false,
+                        const std::function<bool(int index)>& rowDimmed = nullptr) const;
   virtual void drawHeader(const GfxRenderer& renderer, Rect rect, const char* title,
                           const char* subtitle = nullptr) const;
   virtual void drawSubHeader(const GfxRenderer& renderer, Rect rect, const char* label,

src/components/themes/lyra/LyraTheme.cpp

@@ -208,7 +208,8 @@ void LyraTheme::drawList(const GfxRenderer& renderer, Rect rect, int itemCount,
                          const std::function<std::string(int index)>& rowTitle,
                          const std::function<std::string(int index)>& rowSubtitle,
                          const std::function<UIIcon(int index)>& rowIcon,
-                         const std::function<std::string(int index)>& rowValue, bool highlightValue) const {
+                         const std::function<std::string(int index)>& rowValue, bool highlightValue,
+                         const std::function<bool(int index)>& rowDimmed) const {
   int rowHeight =
       (rowSubtitle != nullptr) ? LyraMetrics::values.listWithSubtitleRowHeight : LyraMetrics::values.listRowHeight;
   int pageItems = rect.height / rowHeight;
@@ -267,6 +268,15 @@ void LyraTheme::drawList(const GfxRenderer& renderer, Rect rect, int itemCount,
     auto item = renderer.truncatedText(UI_10_FONT_ID, itemName.c_str(), rowTextWidth);
     renderer.drawText(UI_10_FONT_ID, textX, itemY + 7, item.c_str(), true);
 
+    // Apply checkerboard dither to create gray text effect for dimmed items
+    if (rowDimmed && rowDimmed(i) && i != selectedIndex) {
+      const int titleWidth = renderer.getTextWidth(UI_10_FONT_ID, item.c_str());
+      const int lineH = renderer.getLineHeight(UI_10_FONT_ID);
+      for (int py = itemY + 7; py < itemY + 7 + lineH; py++)
+        for (int px = textX; px < textX + titleWidth; px++)
+          if ((px + py) % 2 == 0) renderer.drawPixel(px, py, false);
+    }
+
     if (rowIcon != nullptr) {
       UIIcon icon = rowIcon(i);
       const uint8_t* iconBitmap = iconForName(icon, iconSize);

src/components/themes/lyra/LyraTheme.h

@@ -59,7 +59,7 @@ class LyraTheme : public BaseTheme {
                 const std::function<std::string(int index)>& rowTitle,
                 const std::function<std::string(int index)>& rowSubtitle,
                 const std::function<UIIcon(int index)>& rowIcon, const std::function<std::string(int index)>& rowValue,
-                bool highlightValue) const override;
+                bool highlightValue, const std::function<bool(int index)>& rowDimmed = nullptr) const override;
   void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
                        const char* btn4) const override;
   void drawSideButtonHints(const GfxRenderer& renderer, const char* topBtn, const char* bottomBtn) const override;

src/components/themes/roundedraff/RoundedRaffTheme.cpp

@@ -247,9 +247,11 @@ void RoundedRaffTheme::drawList(const GfxRenderer& renderer, Rect rect, int item
                                 const std::function<std::string(int index)>& rowTitle,
                                 const std::function<std::string(int index)>& rowSubtitle,
                                 const std::function<UIIcon(int index)>& rowIcon,
-                                const std::function<std::string(int index)>& rowValue, bool highlightValue) const {
+                                const std::function<std::string(int index)>& rowValue, bool highlightValue,
+                                const std::function<bool(int index)>& rowDimmed) const {
   (void)rowIcon;
   (void)highlightValue;
+  (void)rowDimmed;
   const bool hasSubtitle = static_cast<bool>(rowSubtitle);
   const int titleLineHeight = renderer.getLineHeight(kTitleFontId);
   const int subtitleLineHeight = renderer.getLineHeight(kSubtitleFontId);

src/components/themes/roundedraff/RoundedRaffTheme.h

@@ -56,8 +56,8 @@ class RoundedRaffTheme : public BaseTheme {
                 const std::function<std::string(int index)>& rowTitle,
                 const std::function<std::string(int index)>& rowSubtitle = nullptr,
                 const std::function<UIIcon(int index)>& rowIcon = nullptr,
-                const std::function<std::string(int index)>& rowValue = nullptr,
-                bool highlightValue = false) const override;
+                const std::function<std::string(int index)>& rowValue = nullptr, bool highlightValue = false,
+                const std::function<bool(int index)>& rowDimmed = nullptr) const override;
   void drawButtonHints(GfxRenderer& renderer, const char* btn1, const char* btn2, const char* btn3,
                        const char* btn4) const override;
   bool homeMenuShowsContinueReading() const { return true; }