feat: Add central logging pragma (#843)

## Summary

* Definition and use of a central LOG function, that can later be
extended or completely be removed (for public use where debugging
information may not be required) to save flash by suppressing the
-DENABLE_SERIAL_LOG like in the slim branch

* **What changes are included?**

## Additional Context
* By using the central logger the usual:
```
#include <HardwareSerial.h>
...
  Serial.printf("[%lu] [WCS] Obfuscating/deobfuscating %zu bytes\n", millis(), data.size());
```
would then become
```
#include <Logging.h>
...
  LOG_DBG("WCS", "Obfuscating/deobfuscating %zu bytes", data.size());
```
You do have ``LOG_DBG`` for debug messages, ``LOG_ERR`` for error
messages and ``LOG_INF`` for informational messages. Depending on the
verbosity level defined (see below) soe of these message types will be
suppressed/not-compiled.

* The normal compilation (default) will create a firmware.elf file of
42.194.356 bytes, the same code via slim will create 42.024.048 bytes -
170.308 bytes less
* Firmware.bin : 6.469.984 bytes for default, 6.418.672 bytes for slim -
51.312 bytes less


### 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? _NO_

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

src/activities/reader/EpubReaderActivity.cpp

@@ -4,6 +4,7 @@
 #include <FsHelpers.h>
 #include <GfxRenderer.h>
 #include <HalStorage.h>
+#include <Logging.h>
 
 #include "CrossPointSettings.h"
 #include "CrossPointState.h"
@@ -84,7 +85,7 @@ void EpubReaderActivity::onEnter() {
       currentSpineIndex = data[0] + (data[1] << 8);
       nextPageNumber = data[2] + (data[3] << 8);
       cachedSpineIndex = currentSpineIndex;
-      Serial.printf("[%lu] [ERS] Loaded cache: %d, %d\n", millis(), currentSpineIndex, nextPageNumber);
+      LOG_DBG("ERS", "Loaded cache: %d, %d", currentSpineIndex, nextPageNumber);
     }
     if (dataSize == 6) {
       cachedChapterTotalPageCount = data[4] + (data[5] << 8);
@@ -97,8 +98,7 @@ void EpubReaderActivity::onEnter() {
     int textSpineIndex = epub->getSpineIndexForTextReference();
     if (textSpineIndex != 0) {
       currentSpineIndex = textSpineIndex;
-      Serial.printf("[%lu] [ERS] Opened for first time, navigating to text reference at index %d\n", millis(),
-                    textSpineIndex);
+      LOG_DBG("ERS", "Opened for first time, navigating to text reference at index %d", textSpineIndex);
     }
   }
 
@@ -567,7 +567,7 @@ void EpubReaderActivity::renderScreen() {
 
   if (!section) {
     const auto filepath = epub->getSpineItem(currentSpineIndex).href;
-    Serial.printf("[%lu] [ERS] Loading file: %s, index: %d\n", millis(), filepath.c_str(), currentSpineIndex);
+    LOG_DBG("ERS", "Loading file: %s, index: %d", filepath.c_str(), currentSpineIndex);
     section = std::unique_ptr<Section>(new Section(epub, currentSpineIndex, renderer));
 
     const uint16_t viewportWidth = renderer.getScreenWidth() - orientedMarginLeft - orientedMarginRight;
@@ -576,19 +576,19 @@ void EpubReaderActivity::renderScreen() {
     if (!section->loadSectionFile(SETTINGS.getReaderFontId(), SETTINGS.getReaderLineCompression(),
                                   SETTINGS.extraParagraphSpacing, SETTINGS.paragraphAlignment, viewportWidth,
                                   viewportHeight, SETTINGS.hyphenationEnabled, SETTINGS.embeddedStyle)) {
-      Serial.printf("[%lu] [ERS] Cache not found, building...\n", millis());
+      LOG_DBG("ERS", "Cache not found, building...");
 
       const auto popupFn = [this]() { GUI.drawPopup(renderer, "Indexing..."); };
 
       if (!section->createSectionFile(SETTINGS.getReaderFontId(), SETTINGS.getReaderLineCompression(),
                                       SETTINGS.extraParagraphSpacing, SETTINGS.paragraphAlignment, viewportWidth,
                                       viewportHeight, SETTINGS.hyphenationEnabled, SETTINGS.embeddedStyle, popupFn)) {
-        Serial.printf("[%lu] [ERS] Failed to persist page data to SD\n", millis());
+        LOG_ERR("ERS", "Failed to persist page data to SD");
         section.reset();
         return;
       }
     } else {
-      Serial.printf("[%lu] [ERS] Cache found, skipping build...\n", millis());
+      LOG_DBG("ERS", "Cache found, skipping build...");
     }
 
     if (nextPageNumber == UINT16_MAX) {
@@ -622,7 +622,7 @@ void EpubReaderActivity::renderScreen() {
   renderer.clearScreen();
 
   if (section->pageCount == 0) {
-    Serial.printf("[%lu] [ERS] No pages to render\n", millis());
+    LOG_DBG("ERS", "No pages to render");
     renderer.drawCenteredText(UI_12_FONT_ID, 300, "Empty chapter", true, EpdFontFamily::BOLD);
     renderStatusBar(orientedMarginRight, orientedMarginBottom, orientedMarginLeft);
     renderer.displayBuffer();
@@ -630,7 +630,7 @@ void EpubReaderActivity::renderScreen() {
   }
 
   if (section->currentPage < 0 || section->currentPage >= section->pageCount) {
-    Serial.printf("[%lu] [ERS] Page out of bounds: %d (max %d)\n", millis(), section->currentPage, section->pageCount);
+    LOG_DBG("ERS", "Page out of bounds: %d (max %d)", section->currentPage, section->pageCount);
     renderer.drawCenteredText(UI_12_FONT_ID, 300, "Out of bounds", true, EpdFontFamily::BOLD);
     renderStatusBar(orientedMarginRight, orientedMarginBottom, orientedMarginLeft);
     renderer.displayBuffer();
@@ -640,14 +640,14 @@ void EpubReaderActivity::renderScreen() {
   {
     auto p = section->loadPageFromSectionFile();
     if (!p) {
-      Serial.printf("[%lu] [ERS] Failed to load page from SD - clearing section cache\n", millis());
+      LOG_ERR("ERS", "Failed to load page from SD - clearing section cache");
       section->clearCache();
       section.reset();
       return renderScreen();
     }
     const auto start = millis();
     renderContents(std::move(p), orientedMarginTop, orientedMarginRight, orientedMarginBottom, orientedMarginLeft);
-    Serial.printf("[%lu] [ERS] Rendered page in %dms\n", millis(), millis() - start);
+    LOG_DBG("ERS", "Rendered page in %dms", millis() - start);
   }
   saveProgress(currentSpineIndex, section->currentPage, section->pageCount);
 }
@@ -664,9 +664,9 @@ void EpubReaderActivity::saveProgress(int spineIndex, int currentPage, int pageC
     data[5] = (pageCount >> 8) & 0xFF;
     f.write(data, 6);
     f.close();
-    Serial.printf("[%lu] [ERS] Progress saved: Chapter %d, Page %d\n", millis(), spineIndex, currentPage);
+    LOG_DBG("ERS", "Progress saved: Chapter %d, Page %d", spineIndex, currentPage);
   } else {
-    Serial.printf("[%lu] [ERS] Could not save progress!\n", millis());
+    LOG_ERR("ERS", "Could not save progress!");
   }
 }
 void EpubReaderActivity::renderContents(std::unique_ptr<Page> page, const int orientedMarginTop,