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

CONTRIBUTING.md

@@ -0,0 +1,101 @@
+# Contributing to ESP8266 Weather Clock
+
+Thank you for your interest in contributing! This project welcomes improvements, bug fixes, and new features.
+
+## How to Contribute
+
+### Reporting Bugs
+
+If you find a bug, please open an issue with:
+- Clear description of the problem
+- Steps to reproduce
+- Expected vs actual behavior
+- Serial console output (if applicable)
+- Firmware version
+
+### Suggesting Features
+
+Feature requests are welcome! Please include:
+- Use case description
+- Why this would be useful
+- Any implementation ideas
+
+### Pull Requests
+
+1. **Fork the repository**
+2. **Create a feature branch**: `git checkout -b feature/my-new-feature`
+3. **Test your changes**:
+   - Compile successfully
+   - Test on real hardware if possible
+   - Check memory usage (IRAM must stay < 95%)
+4. **Follow the code style**:
+   - Use `ICACHE_FLASH_ATTR` for non-critical functions
+   - Avoid String concatenation in loops
+   - Document state machines with comments
+5. **Commit with clear messages**: Explain what and why, not how
+6. **Submit PR** with description of changes
+
+### Code Guidelines
+
+**Memory Safety:**
+- Check IRAM usage after adding code
+- Use fixed-size buffers instead of dynamic allocation where possible
+- Prefer `snprintf` over String concatenation
+
+**Async Architecture:**
+- Keep loop() non-blocking (no delay() calls)
+- Use state machines for multi-step operations
+- Add exponential backoff to network operations
+
+**Testing:**
+- Test on ESP-01S hardware (1MB flash, 80KB RAM)
+- Verify OTA updates work
+- Check 24h stability
+
+## Development Setup
+
+### Requirements
+- Arduino IDE 1.8.x or 2.x
+- ESP8266 board support (v3.0.0+)
+- Libraries (see README)
+
+### Building
+```bash
+# Arduino IDE: Sketch → Verify/Compile
+# Or use arduino-cli:
+arduino-cli compile --fqbn esp8266:esp8266:generic src/clock_ntp_ota_v1.9.ino
+```
+
+### Testing
+```bash
+# Upload via FTDI (first time)
+arduino-cli upload -p /dev/cu.usbserial* --fqbn esp8266:esp8266:generic
+
+# Upload via OTA (subsequent)
+curl -u admin:admin -F "file=@build/*.bin" http://192.168.x.x/update
+```
+
+## Project Structure
+
+```
+esp8266-weather-clock-opensource/
+├── src/                    # Main firmware source
+├── docs/                   # Documentation
+├── images/                 # Photos and screenshots
+├── README.md               # Main documentation
+└── LICENSE                 # MIT License
+```
+
+## Communication
+
+- **Issues**: Bug reports and feature requests
+- **Discussions**: General questions and ideas
+- **Pull Requests**: Code contributions
+
+## Code of Conduct
+
+Be respectful, constructive, and helpful. We're all here to learn and build cool stuff.
+
+## Questions?
+
+Open an issue or discussion - happy to help!