Fix NAM engine block_size at boot to match audio profile period

- FastNAMHost now initialized with block_size from audio config's
  latency profile (e.g. 512 for stable, 256 for standard)
- Prevents sample-alignment mismatch between JACK period and
  NAM engine internal buffer size at boot

main.py

@@ -133,7 +133,8 @@ class PedalApp:
                 logger.info("JACK disabled in config — skipping audio server start")
 
             # ── 2. DSP pipeline (NAM + IR + FX chain) ────────────
-            self.nam_host = FastNAMHost()
+            block_size = self.audio_config.latency_profile["period"]
+            self.nam_host = FastNAMHost(block_size=block_size)
             self.ir_loader = IRLoader()
             self.pipeline = AudioPipeline(nam_host=self.nam_host, ir_loader=self.ir_loader)
             self.nam_host.warm_up()