Boundary mode: performance optimizations + boundary filter

Performance optimizations:
- Move TLSF allocator pool to PSRAM (frees ~170KB internal SRAM)
- Raise TCP_IF_MAX_CLIENTS from 4 to 8 in BOUNDARY_MODE
- Raise path_table_maxsize from 48 to 128, persist from 16 to 32
- Add -DNDEBUG to boundary build: compiles out TRACE/DEBUG macros
- Log level defaults to LOG_VERBOSE when NDEBUG defined
- Serial baud 115200 -> 921600 in BOUNDARY_MODE (reduces CPU blocking)

Previous changes included in this commit:
- Comprehensive boundary filter with transitive whitelisting (7 checks)
- destination_table erase+insert fix (std::map::insert no-overwrite bug)
- Backbone-to-backbone routing guard in next-hop forwarding
- KISS serial output disabled for boundary mode
- flash.py updates for boundary mode support

platformio.ini

@@ -335,12 +335,14 @@ board_build.partitions = default_16MB.csv
 board_build.flash_mode = qio
 board_build.psram_type = qio
 board_build.arduino.memory_type = qio_qspi
+monitor_speed = 921600
 build_flags = 
 	${env.build_flags}
 	-DBOARD_MODEL=BOARD_HELTEC32_V4
 	-DARDUINO_USB_CDC_ON_BOOT=1
 	-DBOARD_HAS_PSRAM=1
 	-DBOUNDARY_MODE
+	-DNDEBUG
 	; --- Boundary mode defaults (override via EEPROM at runtime) ---
 	; TCP server mode (0=server, 1=client)
 	-DBOUNDARY_TCP_MODE=0