fix: book canonical, fr/de pin warnings, pin grouping per locale, SEO checks

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

data/de/conexoes/ESP32-C2.json

@@ -7,7 +7,7 @@
       "HF-Antennenanschluss (Wi-Fi und Bluetooth)"
     ],
     "categorias": [
-      "Antenne",
+      "Antena",
       "RF"
     ],
     "avisos": [
@@ -301,7 +301,7 @@
       "UART"
     ],
     "avisos": [
-      "UART0 receive pin (Serial RX by default for flashing and monitoring)."
+      "UART0-Empfangs-Pin (standardmäßig serieller RX zum Flashen und Überwachen)."
     ]
   },
   {
@@ -317,7 +317,7 @@
       "UART"
     ],
     "avisos": [
-      "UART0 transmit pin (Serial TX by default for flashing and monitoring)."
+      "UART0-Sende-Pin (standardmäßig serieller TX zum Flashen und Überwachen)."
     ]
   },
   {