slim2Diretta v1.4.8

Fixed

• Boot hang: Target stuck in stale idle-mode when powered on before slim2diretta — port of DirettaRendererUPnP PR #79 (by hoorna/Alfred). When a Diretta Target has been idle for more than a few minutes before slim2diretta starts, it can enter a stuck idle-mode: it accepts the SDK connection but never reaches a streaming-capable state — LEDs blink fast indefinitely and no LMS renderer can claim it. Unlike DirettaRendererUPnP (which had a boot warmup since commit 0d1279b), slim2diretta performed no boot pre-connect at all, so the first open() on the first play request would find the Target stuck. The fix adds the same boot warmup pattern: open(PCM 44.1kHz/24-bit/2ch) → stopPlayback() → sleep(6 s) → release(), giving the Target time to exit its stuck state before the first LMS play command arrives. The first real play then does a fresh cold connect. Trade-off: boot is ~6 s longer, and the first play pays a small cold-connect cost; both are acceptable vs. a renderer that cannot claim the Target at all.
• Version string in binary was stuck at 1.4.6 — the v1.4.7 version bump updated CMakeLists.txt but not src/main.cpp; the --version flag and startup log therefore still showed 1.4.6. Fixed as part of this bump to 1.4.8.