security: replace sprintf/strcpy with bounds-checked variants

[weebl2000]

Summary

• Replaces unsafe sprintf calls with snprintf across multiple modules
• Replaces unsafe strcpy calls with strncpy + null termination
• Prevents potential buffer overflows from untrusted or variable-length input

Changes by file:

File	Issue	Fix
DetectionSensorModule.cpp	sprintf into 40-byte buf with user-configurable sensor name (up to 20 bytes)	snprintf(msg, 40, ...)
DropzoneModule.cpp	sprintf with owner.short_name/long_name from mesh + weather data	snprintf(buf, sizeof(buf), ...)
KeyVerificationModule.cpp	5x sprintf into ClientNotification message buffers	snprintf(cn->message, sizeof(cn->message), ...)
NodeDB.cpp	sprintf warning message with remote long_name (40 bytes)	snprintf(cn->message, sizeof(cn->message), ...)
RedirectablePrint.cpp	strcpy into 384-byte logRecord.message and 32-byte logRecord.source	strncpy + null termination
FSCommon.cpp	strcpy filesystem path into 228-byte fileInfo.file_name	strncpy + null termination
NodeInfoModule.cpp	strcpy node ID into 16-byte u.id	strncpy + null termination

Background

MeshCore's security audit flagged widespread sprintf/strcpy usage without bounds checking. The same pattern exists in Meshtastic. While most buffers are sized adequately for typical data, user-configurable fields (sensor names, node names) and mesh-received data (owner names) could exceed buffer limits.

Test plan

• Verify tbeam build succeeds
• Verify detection sensor messages still send correctly
• Verify dropzone conditions responses format correctly
• Verify key verification UI notifications display correctly
• Verify BLE log records don't truncate normal messages