build(solo): offline queue 128 on the nRF52 builds

The phone app's offline queue took 256 x 177 B = 45 KB, which with the
on-device UI left the L1 ~5 KB of heap from boot (the sign buffer of #38
never fit). The UI keeps its own message history, and a full queue drops
the oldest channel messages first, so 128 is plenty: the L1 heap now has
~27 KB free. L1 OLED / e-ink, ProMicro, T-Echo Lite, both GAT562; the
upstream variants/ are unchanged (build_unflags in solo/).

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

solo/promicro/platformio.ini

@@ -17,14 +17,17 @@ board_build.ldscript = boards/nrf52840_s140_v6_extrafs.ld
 board_upload.maximum_size = 712704
 ; -Ofast (the core's default) doesn't fit a feature-complete solo build;
 ; -Os fits with headroom.
-build_unflags = -Ofast
+; The offline queue (messages held for the phone app while it's away) at 128,
+; not the board's 256: on the nRF52 the 256 x 177 B left ~5 KB of heap next to
+; the on-device UI (which keeps its own history), too little for a sign buffer.
+build_unflags = -Ofast -D OFFLINE_QUEUE_SIZE=256
 build_flags = ${Promicro.build_flags}
   -I examples/companion_radio/ui-new
   -D MAX_CONTACTS=350
   -D MAX_GROUP_CHANNELS=40
   -D BLE_PIN_CODE=123456
   -D DUAL_SERIAL=1
-  -D OFFLINE_QUEUE_SIZE=256
+  -D OFFLINE_QUEUE_SIZE=128
   -D DISPLAY_CLASS=SSD1306Display
   -D FIRMWARE_SOLO_BUILD=1
   -D UI_SENSORS_PAGE=1