feat: UI themes, Lyra (#528)

## Summary

### What is the goal of this PR?

- Visual UI overhaul
- UI theme selection

### What changes are included?

- Added a setting "UI Theme": Classic, Lyra
- The classic theme is the current Crosspoint theme
- The Lyra theme implements these mockups:
https://www.figma.com/design/UhxoV4DgUnfrDQgMPPTXog/Lyra-Theme?node-id=2003-7596&t=4CSOZqf0n9uQMxDt-0
by Discord users yagofarias, ruby and gan_shu
- New functions in GFXRenderer to render rounded rectangles, greyscale
fills (using dithering) and thick lines
- Basic UI components are factored into BaseTheme methods which can be
overridden by each additional theme. Methods that are not overridden
will fallback to BaseTheme behavior. This means any new
features/components in CrossPoint only need to be developed for the
"Classic" BaseTheme.
- Additional themes can easily be developed by the community using this
foundation

![IMG_7649
Medium](https://github.com/user-attachments/assets/b516f5a9-2636-4565-acff-91a25b93b39b)
![IMG_7746
Medium](https://github.com/user-attachments/assets/def41810-ab6e-4952-b40f-b9ce7d62bea8)
![IMG_7651
Medium](https://github.com/user-attachments/assets/518a9a6d-107a-4be3-9533-43a2b64b944b)



## Additional Context

- Only the Home, Library and main Settings screens have been implemented
so far, this will be extended to the transfer screens and chapter
selection screen later on, but we need to get the ball rolling somehow
:)
- Loading extra covers on the home screen in the Lyra theme takes a
little more time (about 2 seconds), I added a loading bar popup (reusing
the Indexing progress bar from the reader view, factored into a neat UI
component) but the popup adds ~400ms to the loading time.
- ~~Home screen thumbnails will need to be generated separately for each
theme, because they are displayed in different sizes. Because we're
using dithering, displaying a thumb with the wrong size causes the
picture to look janky or dark as it does on the screenshots above. No
worries this will be fixed in a future PR.~~ Thumbs are now generated
with a size parameter
- UI Icons will need to be implemented in a future PR.

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? _**PARTIALLY**_
This is not a vibe coded PR. Copilot was used for autocompletion to save
time but I reviewed, understood and edited all generated code.

---------

Co-authored-by: Dave Allie <dave@daveallie.com>

lib/Xtc/Xtc.cpp

@@ -301,11 +301,12 @@ bool Xtc::generateCoverBmp() const {
   return true;
 }
 
-std::string Xtc::getThumbBmpPath() const { return cachePath + "/thumb.bmp"; }
+std::string Xtc::getThumbBmpPath() const { return cachePath + "/thumb_[HEIGHT].bmp"; }
+std::string Xtc::getThumbBmpPath(int height) const { return cachePath + "/thumb_" + std::to_string(height) + ".bmp"; }
 
-bool Xtc::generateThumbBmp() const {
+bool Xtc::generateThumbBmp(int height) const {
   // Already generated
-  if (SdMan.exists(getThumbBmpPath().c_str())) {
+  if (SdMan.exists(getThumbBmpPath(height).c_str())) {
     return true;
   }
 
@@ -333,8 +334,8 @@ bool Xtc::generateThumbBmp() const {
   const uint8_t bitDepth = parser->getBitDepth();
 
   // Calculate target dimensions for thumbnail (fit within 240x400 Continue Reading card)
-  constexpr int THUMB_TARGET_WIDTH = 240;
-  constexpr int THUMB_TARGET_HEIGHT = 400;
+  int THUMB_TARGET_WIDTH = height * 0.6;
+  int THUMB_TARGET_HEIGHT = height;
 
   // Calculate scale factor
   float scaleX = static_cast<float>(THUMB_TARGET_WIDTH) / pageInfo.width;
@@ -348,7 +349,7 @@ bool Xtc::generateThumbBmp() const {
     if (generateCoverBmp()) {
       FsFile src, dst;
       if (SdMan.openFileForRead("XTC", getCoverBmpPath(), src)) {
-        if (SdMan.openFileForWrite("XTC", getThumbBmpPath(), dst)) {
+        if (SdMan.openFileForWrite("XTC", getThumbBmpPath(height), dst)) {
           uint8_t buffer[512];
           while (src.available()) {
             size_t bytesRead = src.read(buffer, sizeof(buffer));
@@ -359,7 +360,7 @@ bool Xtc::generateThumbBmp() const {
         src.close();
       }
       Serial.printf("[%lu] [XTC] Copied cover to thumb (no scaling needed)\n", millis());
-      return SdMan.exists(getThumbBmpPath().c_str());
+      return SdMan.exists(getThumbBmpPath(height).c_str());
     }
     return false;
   }
@@ -393,7 +394,7 @@ bool Xtc::generateThumbBmp() const {
 
   // Create thumbnail BMP file - use 1-bit format for fast home screen rendering (no gray passes)
   FsFile thumbBmp;
-  if (!SdMan.openFileForWrite("XTC", getThumbBmpPath(), thumbBmp)) {
+  if (!SdMan.openFileForWrite("XTC", getThumbBmpPath(height), thumbBmp)) {
     Serial.printf("[%lu] [XTC] Failed to create thumb BMP file\n", millis());
     free(pageBuffer);
     return false;
@@ -558,7 +559,7 @@ bool Xtc::generateThumbBmp() const {
   free(pageBuffer);
 
   Serial.printf("[%lu] [XTC] Generated thumb BMP (%dx%d): %s\n", millis(), thumbWidth, thumbHeight,
-                getThumbBmpPath().c_str());
+                getThumbBmpPath(height).c_str());
   return true;
 }