Phase 1-4: Audio stack, mixer engine, MIDI, and network API

P2-R1: ALSA + JACK2 low-latency config (scripts, quirks, tuning)
P2-R2: Carla integration (build scripts, 8ch rack config, NAM LV2 support)
P2-R3: Plugin manager, categories, blacklist, NAM model support
P3-R1: Mixer DSP engine (channel strip, routing matrix, bus mgr, automation)
P4-R1: MIDI engine (learn mode, clock sync, HID discovery, mapping store)
P4-R2: Network API (OSC server, FastAPI REST, WebSocket, auth, rate limiter)
P5-R1: Touchscreen UI evaluation + main entry point
docs: Audio stack, Carla integration, MIDI support, UI evaluation
tests: Full test suite (292 passing)

tests/conftest.py

@@ -0,0 +1,9 @@
+"""Test configuration for the RPi Audio Mixer test suite."""
+
+import sys
+from pathlib import Path
+
+# Ensure the project root is in sys.path for imports
+_project_root = Path(__file__).resolve().parent.parent
+if str(_project_root) not in sys.path:
+    sys.path.insert(0, str(_project_root))