Initial commit: v1.9.1 production firmware

Complete reverse engineering of TJ-56-654 weather clock from AliExpress.

Security fixes:
- Eliminated WiFi password leak vulnerability
- Removed dependency on Chinese cloud services (QWeather)
- Secure WiFiManager captive portal setup
- No hardcoded credentials

Features:
- Fully async architecture (zero blocking operations)
- OTA firmware updates (web + ArduinoOTA)
- NTP time sync with timezone + DST support
- Open-Meteo weather API (free, no registration)
- 3 display modes: time, weather, sunrise/sunset
- REST API + web interface
- EEPROM config persistence

Performance:
- Loop time: <1ms (was 10ms+)
- Memory: 409KB flash (38%), 38KB RAM (46%), 62KB IRAM (94%)
- Zero blocking delays

Hardware:
- ESP-01S (ESP8266EX, 1MB flash)
- GM009605v4.3 OLED display (128x64, I2C)
- Custom I2C mapping: SDA=GPIO0, SCL=GPIO2

Documentation:
- Complete installation guide
- Hardware specifications
- API documentation
- Troubleshooting guide
- Version history v1.5 → v1.9.1

Built with Claude Code (Opus 4.5)
Author: Andrey Petrochenko
Date: 2026-01-03

.github/workflows/build.yml

@@ -0,0 +1,73 @@
+name: Build Firmware
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  release:
+    types: [ created ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v3
+
+    - name: Setup Arduino CLI
+      uses: arduino/setup-arduino-cli@v1
+
+    - name: Install ESP8266 platform
+      run: |
+        arduino-cli core update-index
+        arduino-cli core install esp8266:esp8266
+
+    - name: Install libraries
+      run: |
+        arduino-cli lib install "Adafruit GFX Library"
+        arduino-cli lib install "Adafruit SSD1306"
+        arduino-cli lib install "NTPClient"
+        arduino-cli lib install "WiFiManager"
+        arduino-cli lib install "AsyncHTTPRequest_Generic"
+        arduino-cli lib install "ESPAsyncTCP"
+
+    - name: Compile firmware
+      run: |
+        arduino-cli compile --fqbn esp8266:esp8266:generic \
+          --build-property "build.flash_size=1M64" \
+          --build-property "build.flash_mode=dio" \
+          --output-dir build \
+          src/clock_ntp_ota_v1.9.ino
+
+    - name: Check firmware size
+      run: |
+        SIZE=$(stat -c%s "build/clock_ntp_ota_v1.9.ino.bin")
+        echo "Firmware size: $SIZE bytes"
+        MAX_SIZE=470000  # 470KB max for OTA
+        if [ $SIZE -gt $MAX_SIZE ]; then
+          echo "ERROR: Firmware too large ($SIZE > $MAX_SIZE)"
+          exit 1
+        fi
+
+    - name: Upload build artifacts
+      uses: actions/upload-artifact@v3
+      with:
+        name: firmware
+        path: |
+          build/clock_ntp_ota_v1.9.ino.bin
+          build/clock_ntp_ota_v1.9.ino.elf
+          build/clock_ntp_ota_v1.9.ino.map
+        retention-days: 30
+
+    - name: Upload release assets
+      if: github.event_name == 'release'
+      uses: actions/upload-release-asset@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ github.event.release.upload_url }}
+        asset_path: build/clock_ntp_ota_v1.9.ino.bin
+        asset_name: esp8266-weather-clock-${{ github.event.release.tag_name }}.bin
+        asset_content_type: application/octet-stream