Fix Python default port assignment from 5000 to 3000

Changed the default port assignment for Python programs in auto-discovery
from 5000 to 3000 to align with the standard port range (3000-3999).
This ensures forensic_cpa_ai and other Python services use ports in the
correct range instead of defaulting to 5000.

https://claude.ai/code/session_01TxioM4AYTvC4DymoDyFZzC

Author: claude

local_nexus_controller/services/auto_discovery.py

@@ -38,7 +38,7 @@ def get_default_port(program_type: str, existing_ports: set[int]) -> int:
     """Get a default port based on program type, avoiding conflicts."""
     base_ports = {
         "nodejs": 3000,
-        "python": 5000,
+        "python": 3000,
         "go": 8080,
         "rust": 8000,
         "java": 8080,