Calibre Web Epub Downloading + Calibre Wireless Device Syncing (#219)

## Summary

Adds support for browsing and downloading books from a Calibre-web
server via OPDS.
How it works
1. Configure server URL in Settings → Calibre Web URL (e.g.,
https://myserver.com:port I use Cloudflare tunnel to make my server
accessible anywhere fwiw)
2. "Calibre Library" will now show on the the home screen
3. Browse the catalog - navigate through categories like "By Newest",
"By Author", "By Series", etc.
4. Download books - select a book and press Confirm to download the EPUB
to your device
Navigation
- Up/Down - Move through entries
- Confirm - Open folder or download book
- Back - Go to parent catalog, or exit to home if at root
- Navigation entries show with > prefix, books show title and author
- Button hints update dynamically ("Open" for folders, "Download" for
books)
Technical details
- Fetches OPDS catalog from {server_url}/opds
- Parses both navigation feeds (catalog links) and acquisition feeds
(downloadable books)
- Maintains navigation history stack for back navigation
- Handles absolute paths in OPDS links correctly (e.g.,
/books/opds/navcatalog/...)
- Downloads EPUBs directly to the SD card root
Note
The server URL should be typed to include https:// if the server
requires it - HTTP→HTTPS redirects may cause SSL errors on ESP32.

## Additional Context

* I also changed the home titles to use uppercase for each word and
added a setting to change the size of the side margins

---------

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

src/main.cpp

@@ -7,12 +7,15 @@
 #include <SPI.h>
 #include <builtinFonts/all.h>
 
+#include <cstring>
+
 #include "Battery.h"
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
 #include "MappedInputManager.h"
 #include "activities/boot_sleep/BootActivity.h"
 #include "activities/boot_sleep/SleepActivity.h"
+#include "activities/browser/OpdsBookBrowserActivity.h"
 #include "activities/home/HomeActivity.h"
 #include "activities/network/CrossPointWebServerActivity.h"
 #include "activities/reader/ReaderActivity.h"
@@ -222,10 +225,15 @@ void onGoToSettings() {
   enterNewActivity(new SettingsActivity(renderer, mappedInputManager, onGoHome));
 }
 
+void onGoToBrowser() {
+  exitActivity();
+  enterNewActivity(new OpdsBookBrowserActivity(renderer, mappedInputManager, onGoHome));
+}
+
 void onGoHome() {
   exitActivity();
   enterNewActivity(new HomeActivity(renderer, mappedInputManager, onContinueReading, onGoToReaderHome, onGoToSettings,
-                                    onGoToFileTransfer));
+                                    onGoToFileTransfer, onGoToBrowser));
 }
 
 void setupDisplayAndFonts() {