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>

lib/Txt/Txt.cpp

@@ -2,6 +2,7 @@
 
 #include <FsHelpers.h>
 #include <JpegToBmpConverter.h>
+#include <Logging.h>
 
 Txt::Txt(std::string path, std::string cacheBasePath)
     : filepath(std::move(path)), cacheBasePath(std::move(cacheBasePath)) {
@@ -16,13 +17,13 @@ bool Txt::load() {
   }
 
   if (!Storage.exists(filepath.c_str())) {
-    Serial.printf("[%lu] [TXT] File does not exist: %s\n", millis(), filepath.c_str());
+    LOG_ERR("TXT", "File does not exist: %s", filepath.c_str());
     return false;
   }
 
   FsFile file;
   if (!Storage.openFileForRead("TXT", filepath, file)) {
-    Serial.printf("[%lu] [TXT] Failed to open file: %s\n", millis(), filepath.c_str());
+    LOG_ERR("TXT", "Failed to open file: %s", filepath.c_str());
     return false;
   }
 
@@ -30,7 +31,7 @@ bool Txt::load() {
   file.close();
 
   loaded = true;
-  Serial.printf("[%lu] [TXT] Loaded TXT file: %s (%zu bytes)\n", millis(), filepath.c_str(), fileSize);
+  LOG_DBG("TXT", "Loaded TXT file: %s (%zu bytes)", filepath.c_str(), fileSize);
   return true;
 }
 
@@ -74,7 +75,7 @@ std::string Txt::findCoverImage() const {
   for (const auto& ext : extensions) {
     std::string coverPath = folder + "/" + baseName + ext;
     if (Storage.exists(coverPath.c_str())) {
-      Serial.printf("[%lu] [TXT] Found matching cover image: %s\n", millis(), coverPath.c_str());
+      LOG_DBG("TXT", "Found matching cover image: %s", coverPath.c_str());
       return coverPath;
     }
   }
@@ -85,7 +86,7 @@ std::string Txt::findCoverImage() const {
     for (const auto& ext : extensions) {
       std::string coverPath = folder + "/" + std::string(name) + ext;
       if (Storage.exists(coverPath.c_str())) {
-        Serial.printf("[%lu] [TXT] Found fallback cover image: %s\n", millis(), coverPath.c_str());
+        LOG_DBG("TXT", "Found fallback cover image: %s", coverPath.c_str());
         return coverPath;
       }
     }
@@ -104,7 +105,7 @@ bool Txt::generateCoverBmp() const {
 
   std::string coverImagePath = findCoverImage();
   if (coverImagePath.empty()) {
-    Serial.printf("[%lu] [TXT] No cover image found for TXT file\n", millis());
+    LOG_DBG("TXT", "No cover image found for TXT file");
     return false;
   }
 
@@ -120,7 +121,7 @@ bool Txt::generateCoverBmp() const {
 
   if (isBmp) {
     // Copy BMP file to cache
-    Serial.printf("[%lu] [TXT] Copying BMP cover image to cache\n", millis());
+    LOG_DBG("TXT", "Copying BMP cover image to cache");
     FsFile src, dst;
     if (!Storage.openFileForRead("TXT", coverImagePath, src)) {
       return false;
@@ -136,13 +137,13 @@ bool Txt::generateCoverBmp() const {
     }
     src.close();
     dst.close();
-    Serial.printf("[%lu] [TXT] Copied BMP cover to cache\n", millis());
+    LOG_DBG("TXT", "Copied BMP cover to cache");
     return true;
   }
 
   if (isJpg) {
     // Convert JPG/JPEG to BMP (same approach as Epub)
-    Serial.printf("[%lu] [TXT] Generating BMP from JPG cover image\n", millis());
+    LOG_DBG("TXT", "Generating BMP from JPG cover image");
     FsFile coverJpg, coverBmp;
     if (!Storage.openFileForRead("TXT", coverImagePath, coverJpg)) {
       return false;
@@ -156,16 +157,16 @@ bool Txt::generateCoverBmp() const {
     coverBmp.close();
 
     if (!success) {
-      Serial.printf("[%lu] [TXT] Failed to generate BMP from JPG cover image\n", millis());
+      LOG_ERR("TXT", "Failed to generate BMP from JPG cover image");
       Storage.remove(getCoverBmpPath().c_str());
     } else {
-      Serial.printf("[%lu] [TXT] Generated BMP from JPG cover image\n", millis());
+      LOG_DBG("TXT", "Generated BMP from JPG cover image");
     }
     return success;
   }
 
   // PNG files are not supported (would need a PNG decoder)
-  Serial.printf("[%lu] [TXT] Cover image format not supported (only BMP/JPG/JPEG)\n", millis());
+  LOG_ERR("TXT", "Cover image format not supported (only BMP/JPG/JPEG)");
   return false;
 }