v0.6.0

Climate entity support for thermostats and HVAC.

• Automatic climate.* entity detection
• Computed attributes: temp_difference and temp_offset for easy visualization
• Smart offset behavior: understands heating vs cooling mode goals
• HVAC action coloring with color.hvac config (heating/cooling/idle/off)
• Dynamic icons based on HVAC state (fire for heating, snowflake for cooling)