feat: Implement IPC backend for real-time UI synchronization

Add KiCAD IPC API backend using kicad-python library for real-time
communication with KiCAD 9.0+. Changes now appear instantly in KiCAD
UI without manual reload.

Key changes:
- Implement IPCBackend and IPCBoardAPI classes for IPC communication
- Auto-detect IPC availability and fall back to SWIG when unavailable
- Route existing commands (route_trace, add_via, place_component, etc.)
  through IPC automatically when available
- Add transaction support for proper undo/redo
- Add socket path auto-detection for Linux (/tmp/kicad/api.sock)

New commands:
- get_backend_info: Check which backend is active

Supported IPC operations:
- Board: set_size, get_board_info, save
- Routing: route_trace, add_via, add_net
- Components: place, move, delete, list
- Text: add_text, add_board_text

SWIG backend is now deprecated and will be removed when KiCAD 10.0
drops SWIG support.

Requires: kicad-python>=0.5.0, KiCAD 9.0+ with IPC enabled

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

python/kicad_api/factory.py

@@ -157,12 +157,12 @@ def get_available_backends() -> dict:
     """
     results = {}
 
-    # Check IPC
+    # Check IPC (kicad-python uses 'kipy' module name)
     try:
-        import kicad
+        import kipy
         results['ipc'] = {
             'available': True,
-            'version': getattr(kicad, '__version__', 'unknown')
+            'version': getattr(kipy, '__version__', 'unknown')
         }
     except ImportError:
         results['ipc'] = {'available': False, 'version': None}