Initial tablet POC: project restructure + WebSocket/HTTP server + JS client

- Restructured project into /app, /server, /client with run.py entry point
- WSServer (QWebSocketServer) with log_signal, start/stop, client tracking
- HTTP server serves /client on port 8080
- Vanilla JS client: faders, toggles, transport, drag-to-arrange, lock/save layout
- Start Tablet button + floating Tablet log window in app UI
- Preset broadcast on load/switch, DAW state relay, hardware sync via widget_update
- Widget colors synced from app palette, toggle state fixed (sends 0/127 correctly)
- Layout saved per preset UUID back to presets.json

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/midi_receiver.py

@@ -0,0 +1,11 @@
+from PyQt6.QtCore import QObject, pyqtSignal
+
+class MidiReceiver(QObject):
+    midi_in_signal = pyqtSignal(list)
+    midi_out_signal = pyqtSignal(list)
+    transport_out_signal = pyqtSignal()
+    hw_cc_signal = pyqtSignal(str, int)
+
+midi_receiver = MidiReceiver()
+
+