refactor: Removed SdCardFontGlobals.h (#1962)

## Summary

First of several changes to decouple and clean up SD card fonts
integration. This change eliminates SdCardFontGlobals.h:
- Simply declare the `extern SdCardFontSystem sdFontSystem` in
SdCardFontSystem.h.
- `ActivityManager::goToReader` should not care about loading SD card
fonts. Instead do the same work in `ReaderActivity::onEnter`, after the
previous activity has exited and after ReaderActivity has validated the
file path.

---

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src/SdCardFontGlobals.h

@@ -1,12 +0,0 @@
-#pragma once
-
-#include "SdCardFontSystem.h"
-
-class GfxRenderer;
-
-// Global SD card font system instance (defined in main.cpp).
-extern SdCardFontSystem sdFontSystem;
-
-// Ensure the correct SD card font family is loaded for current settings.
-// Defined in main.cpp; call before entering the reader or after settings change.
-extern void ensureSdFontLoaded();

src/SdCardFontSystem.h

@@ -50,3 +50,6 @@ class SdCardFontSystem {
   SdCardFontManager manager_;
   std::atomic<bool> registryDirty_{false};
 };
+
+// Global SD card font system instance (defined in main.cpp).
+extern SdCardFontSystem sdFontSystem;

src/activities/ActivityManager.cpp

@@ -5,7 +5,6 @@
 #include <algorithm>
 
 #include "OpdsServerStore.h"
-#include "SdCardFontGlobals.h"
 #include "boot_sleep/BootActivity.h"
 #include "boot_sleep/SleepActivity.h"
 #include "browser/OpdsBookBrowserActivity.h"
@@ -194,7 +193,6 @@ void ActivityManager::goToBrowser() {
 }
 
 void ActivityManager::goToReader(std::string path) {
-  ensureSdFontLoaded();
   replaceActivity(std::make_unique<ReaderActivity>(renderer, mappedInput, std::move(path)));
 }
 

src/activities/reader/ReaderActivity.cpp

@@ -6,6 +6,7 @@
 #include "CrossPointSettings.h"
 #include "Epub.h"
 #include "EpubReaderActivity.h"
+#include "SdCardFontSystem.h"
 #include "Txt.h"
 #include "TxtReaderActivity.h"
 #include "Xtc.h"
@@ -103,6 +104,8 @@ void ReaderActivity::onEnter() {
     return;
   }
 
+  sdFontSystem.ensureLoaded(renderer);
+
   currentBookPath = initialBookPath;
   if (isBmpFile(initialBookPath)) {
     onGoToBmpViewer(initialBookPath);

src/activities/settings/FontDownloadActivity.cpp

@@ -9,7 +9,7 @@
 #include <esp_rom_crc.h>
 
 #include "MappedInputManager.h"
-#include "SdCardFontGlobals.h"
+#include "SdCardFontSystem.h"
 #include "activities/network/WifiSelectionActivity.h"
 #include "activities/util/ConfirmationActivity.h"
 #include "components/UITheme.h"

src/activities/settings/SettingsActivity.cpp

@@ -13,7 +13,7 @@
 #include "MappedInputManager.h"
 #include "OpdsServerListActivity.h"
 #include "OtaUpdateActivity.h"
-#include "SdCardFontGlobals.h"
+#include "SdCardFontSystem.h"
 #include "SdFirmwareUpdateActivity.h"
 #include "SettingsList.h"
 #include "StatusBarSettingsActivity.h"

src/main.cpp

@@ -197,8 +197,6 @@ void enterDeepSleep() {
   powerManager.startDeepSleep(gpio);
 }
 
-void ensureSdFontLoaded() { sdFontSystem.ensureLoaded(renderer); }
-
 void setupDisplayAndFonts() {
   display.begin();
   renderer.begin();

src/network/CrossPointWebServer.cpp

@@ -13,7 +13,6 @@
 #include "CrossPointSettings.h"
 #include "FontInstaller.h"
 #include "OpdsServerStore.h"
-#include "SdCardFontGlobals.h"
 #include "SdCardFontSystem.h"
 #include "SettingsList.h"
 #include "WebDAVHandler.h"