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/KOReaderSyncActivity.cpp

@@ -1,6 +1,7 @@
 #include "KOReaderSyncActivity.h"
 
 #include <GfxRenderer.h>
+#include <Logging.h>
 #include <WiFi.h>
 #include <esp_sntp.h>
 
@@ -32,9 +33,9 @@ void syncTimeWithNTP() {
   }
 
   if (retry < maxRetries) {
-    Serial.printf("[%lu] [KOSync] NTP time synced\n", millis());
+    LOG_DBG("KOSync", "NTP time synced");
   } else {
-    Serial.printf("[%lu] [KOSync] NTP sync timeout, using fallback\n", millis());
+    LOG_DBG("KOSync", "NTP sync timeout, using fallback");
   }
 }
 }  // namespace
@@ -48,12 +49,12 @@ void KOReaderSyncActivity::onWifiSelectionComplete(const bool success) {
   exitActivity();
 
   if (!success) {
-    Serial.printf("[%lu] [KOSync] WiFi connection failed, exiting\n", millis());
+    LOG_DBG("KOSync", "WiFi connection failed, exiting");
     onCancel();
     return;
   }
 
-  Serial.printf("[%lu] [KOSync] WiFi connected, starting sync\n", millis());
+  LOG_DBG("KOSync", "WiFi connected, starting sync");
 
   xSemaphoreTake(renderingMutex, portMAX_DELAY);
   state = SYNCING;
@@ -88,7 +89,7 @@ void KOReaderSyncActivity::performSync() {
     return;
   }
 
-  Serial.printf("[%lu] [KOSync] Document hash: %s\n", millis(), documentHash.c_str());
+  LOG_DBG("KOSync", "Document hash: %s", documentHash.c_str());
 
   xSemaphoreTake(renderingMutex, portMAX_DELAY);
   statusMessage = "Fetching remote progress...";
@@ -188,12 +189,12 @@ void KOReaderSyncActivity::onEnter() {
   }
 
   // Turn on WiFi
-  Serial.printf("[%lu] [KOSync] Turning on WiFi...\n", millis());
+  LOG_DBG("KOSync", "Turning on WiFi...");
   WiFi.mode(WIFI_STA);
 
   // Check if already connected
   if (WiFi.status() == WL_CONNECTED) {
-    Serial.printf("[%lu] [KOSync] Already connected to WiFi\n", millis());
+    LOG_DBG("KOSync", "Already connected to WiFi");
     state = SYNCING;
     statusMessage = "Syncing time...";
     updateRequired = true;
@@ -216,7 +217,7 @@ void KOReaderSyncActivity::onEnter() {
   }
 
   // Launch WiFi selection subactivity
-  Serial.printf("[%lu] [KOSync] Launching WifiSelectionActivity...\n", millis());
+  LOG_DBG("KOSync", "Launching WifiSelectionActivity...");
   enterNewActivity(new WifiSelectionActivity(renderer, mappedInput,
                                              [this](const bool connected) { onWifiSelectionComplete(connected); }));
 }