List of changes

• {fmt} is now a required repository fetched from CMake. The static library will be automatically built and linked.
• Updated r8brain-free-src to Version 7.1; CMakefile.txt was updated as well.
• Changed CW/USB/LSB FIR filters not to down/up-convert between 48kHz and 12kHz sampling rates, and to use the 2049-tap filters of 48ksamples/sec. This significantly reduced output latency, tolerable for interactive use (such as FT8 reception). The CPU usage increased ~4 times than before, but was still in acceptable range (~60% of FM -E 100 setting).
• File permission mode for the sound file output and the ppsfile is explicitly set to 0600 instead of 0666.
• Refactored non-owning raw pointers to unique pointers.

Full Changelog: https://github.com/jj1bdx/airspy-fmradion/compare/20250929-0...20260211-0