Release v1.5.3: Fix thermal sensor bug & update D-Bus policies

• Bump version to v1.5.3 across all configuration and source files.
• Fix an issue in platform_service.py where disconnected or unsupported ACPI thermal sensors reported absolute zero. Temperatures below -100 °C are now correctly ignored.
• Relax D-Bus security policies (*.conf) for all microservices (fan, platform, mux, power, rgb). Standard unprivileged users now have full read/write access to control hardware states and view metrics via the GUI without requiring sudo or wheel group membership.