feat: add ESP8266 support + Akaso camera compatibility config

- Unified firmware for ESP32 (dual-STA) and ESP8266 (time-shared STA)
- ESP8266: alternates between GoPro AP and travel router per poll cycle
- PlatformIO dual-target: esp32dev + esp8266dev (d1_mini)
- camera_ip config field for Akaso/non-GoPro cameras
- LittleFS support for ESP8266 (replaces SPIFFS)
- Camera compatibility table (GoPro H3/H4, Akaso)
- LED polarity handled per-platform (ESP8266 active-low)

ESP8266 time-sharing adds ~4s latency per 30s cycle — invisible at poll rate.

firmware/platformio.ini

@@ -1,11 +1,24 @@
-; RemoteRig — ESP32 Camera Node Firmware
-; Platform: ESP32 (ESP8266 compatible with minor changes)
-; Framework: Arduino
+; RemoteRig — ESP32 + ESP8266 Camera Node Firmware
+; PlatformIO project with dual-target support.
 ;
-; Build:  pio run
-; Upload: pio run --target upload
-; SPIFFS: pio run --target uploadfs
-; Monitor: pio device monitor
+; Build:
+;   pio run -e esp32dev     (ESP32 Dev Board — dual-STA, recommended)
+;   pio run -e esp8266dev   (ESP8266 D1 Mini — time-shared STA)
+;
+; Upload:
+;   pio run -e esp32dev --target upload
+;   pio run -e esp8266dev --target upload
+;
+; SPIFFS/LittleFS:
+;   pio run -e esp32dev --target uploadfs
+;   pio run -e esp8266dev --target uploadfs
+
+[common]
+lib_deps =
+    knolleary/PubSubClient @ ^2.8
+    bblanchon/ArduinoJson @ ^7.3
+build_flags =
+    -D CORE_DEBUG_LEVEL=0
 
 [env:esp32dev]
 platform = espressif32
@@ -13,11 +26,19 @@ board = esp32dev
 framework = arduino
 monitor_speed = 115200
 upload_speed = 921600
-
-lib_deps =
-    knolleary/PubSubClient @ ^2.8
-    bblanchon/ArduinoJson @ ^7.3
-
-build_flags =
-    -D CORE_DEBUG_LEVEL=0
+lib_deps = ${common.lib_deps}
+build_flags = ${common.build_flags}
     -D CONFIG_ARDUINO_LOOP_STACK_SIZE=8192
+
+[env:esp8266dev]
+platform = espressif8266
+board = d1_mini
+framework = arduino
+monitor_speed = 115200
+upload_speed = 921600
+lib_deps = ${common.lib_deps}
+build_flags = ${common.build_flags}
+    -D PIO_FRAMEWORK_ARDUINO_MMU_CACHE16_IRAM48_SECHEAP_SHARED
+    -D CONFIG_ARDUINO_LOOP_STACK_SIZE=8192
+board_build.flash_mode = dio
+board_build.f_cpu = 160000000L