Add JP_STRICT mode: enforce MAX_TEXT_LEN for ARIB STD-T108 compliance

JP_STRICT limits MAX_TEXT_LEN to 1*CIPHER_BLOCK_SIZE (16 bytes) to keep
TX time under 4 seconds on SF12/BW125/CR4-8 (Japan LoRa settings).

SF12/BW125/CR4-8 airtime:
  60 bytes total packet = ~3809ms (within 4s limit)
  packet overhead ~44 bytes, leaving 16 bytes for text payload

Enabled only for WioTrackerL1 and RAK_WisMesh_Tag builds.

src/helpers/BaseChatMesh.h

@@ -5,7 +5,14 @@
 #include <helpers/AdvertDataHelpers.h>
 #include <helpers/TxtDataHelpers.h>
 
-#define MAX_TEXT_LEN    (10*CIPHER_BLOCK_SIZE)  // must be LESS than (MAX_PACKET_PAYLOAD - 4 - CIPHER_MAC_SIZE - 1)
+// JP_STRICT: limit MAX_TEXT_LEN to keep TX time under 4s (ARIB STD-T108)
+// SF12/BW125/CR4-8: 60 bytes total packet = ~3809ms, overhead ~44 bytes
+// leaving 16 bytes (1*CIPHER_BLOCK_SIZE) for text payload
+#ifdef JP_STRICT
+  #define MAX_TEXT_LEN  (1*CIPHER_BLOCK_SIZE)   // ~16 chars, TX <= 4s for JP
+#else
+  #define MAX_TEXT_LEN  (10*CIPHER_BLOCK_SIZE)  // must be LESS than (MAX_PACKET_PAYLOAD - 4 - CIPHER_MAC_SIZE - 1)
+#endif
 
 #include "ContactInfo.h"
 

variants/rak_wismesh_tag/platformio.ini

@@ -25,6 +25,7 @@ build_flags = ${nrf52_base.build_flags}
   -D PIN_BUZZER=21
   -D PIN_BOARD_SDA=PIN_WIRE_SDA
   -D PIN_BOARD_SCL=PIN_WIRE_SCL
+  -D JP_STRICT
 build_src_filter = ${nrf52_base.build_src_filter}
   +<../variants/rak_wismesh_tag>
   +<helpers/ui/MomentaryButton.cpp>
@@ -118,4 +119,4 @@ build_flags =
 ;  -D MESH_PACKET_LOGGING=1
   -D MESH_DEBUG=1
 build_src_filter = ${rak4631.build_src_filter}
-  +<../examples/simple_sensor>
+  +<../examples/simple_sensor>

variants/wio-tracker-l1/platformio.ini

@@ -16,6 +16,7 @@ build_flags = ${nrf52_base.build_flags}
   -D SX126X_RX_BOOSTED_GAIN=1
   -D PIN_OLED_RESET=-1
   -D GPS_BAUD_RATE=9600
+  -D JP_STRICT
 build_src_filter = ${nrf52_base.build_src_filter}
   +<WioTrackerL1Board.cpp>
   +<../variants/wio-tracker-l1>