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/activities/settings/CalibreSettingsActivity.h

@@ -0,0 +1,36 @@
+#pragma once
+#include <freertos/FreeRTOS.h>
+#include <freertos/semphr.h>
+#include <freertos/task.h>
+
+#include <functional>
+
+#include "activities/ActivityWithSubactivity.h"
+
+/**
+ * Submenu for Calibre settings.
+ * Shows Calibre Web URL and Calibre Wireless Device options.
+ */
+class CalibreSettingsActivity final : public ActivityWithSubactivity {
+ public:
+  explicit CalibreSettingsActivity(GfxRenderer& renderer, MappedInputManager& mappedInput,
+                                   const std::function<void()>& onBack)
+      : ActivityWithSubactivity("CalibreSettings", renderer, mappedInput), onBack(onBack) {}
+
+  void onEnter() override;
+  void onExit() override;
+  void loop() override;
+
+ private:
+  TaskHandle_t displayTaskHandle = nullptr;
+  SemaphoreHandle_t renderingMutex = nullptr;
+  bool updateRequired = false;
+
+  int selectedIndex = 0;
+  const std::function<void()> onBack;
+
+  static void taskTrampoline(void* param);
+  [[noreturn]] void displayTaskLoop();
+  void render();
+  void handleSelection();
+};