fix(display): default the R8 portrait panels to DISPLAY_ROTATION=0

Rotation 2 was consistently upside down on the Expansion Kit V2 panel, so 0
becomes the compiled default for both portrait observer targets.

display.flip is unchanged and still defaults to off: the compiled constant
should be the correct orientation, with the setting reserved for a board
mounted the other way up. A node already carrying `display.flip 1` from
testing needs `set display.flip 0` after this.

Landscape targets are untouched - they take the driver's own DISPLAY_ROTATION
default of 3.

variants/heltec_v4_r8/platformio.ini

@@ -369,7 +369,9 @@ extends = env:heltec_v4_r8_tft_repeater_observer_mqtt
 build_flags =
   ${env:heltec_v4_r8_tft_repeater_observer_mqtt.build_flags}
   -D ST7789_PORTRAIT_PROFILE=1
-  -D DISPLAY_ROTATION=2
+; Verified upright on the Expansion Kit V2 panel. `set display.flip 1` turns it
+; 180 degrees for a board mounted the other way up.
+  -D DISPLAY_ROTATION=0
 
 [env:heltec_v4_r8_tft_room_server]
 extends = heltec_v4_r8_tft
@@ -448,7 +450,9 @@ extends = env:heltec_v4_r8_tft_room_server_observer_mqtt
 build_flags =
   ${env:heltec_v4_r8_tft_room_server_observer_mqtt.build_flags}
   -D ST7789_PORTRAIT_PROFILE=1
-  -D DISPLAY_ROTATION=2
+; Verified upright on the Expansion Kit V2 panel. `set display.flip 1` turns it
+; 180 degrees for a board mounted the other way up.
+  -D DISPLAY_ROTATION=0
 
 [env:heltec_v4_r8_tft_terminal_chat]
 extends = heltec_v4_r8_tft