fix: Correct all NX installation paths from Simcenter3D_2412 to NX2412

CRITICAL PATH CORRECTION:
- Updated all documentation to use NX2412 installation
- Fixed README.md, dashboard/api/app.py, NXOPEN_INTELLISENSE_SETUP.md
- Updated archived NX_SOLVER_INTEGRATION.md for consistency
- Added SYSTEM_CONFIGURATION.md to document correct paths

Files Changed:
- README.md: NX path corrected to NX2412\NXBIN\run_journal.exe
- dashboard/api/app.py: NX executable path updated
- docs/NXOPEN_INTELLISENSE_SETUP.md: Stub path corrected
- docs/archive/NX_SOLVER_INTEGRATION.md: Example paths updated
- docs/SYSTEM_CONFIGURATION.md: NEW - Critical system path documentation

Key Configuration:
- Python Environment: atomizer (NOT test_env)
- NX Installation: C:\Program Files\Siemens\NX2412
- Material Library: NX2412\UGII\materials\physicalmateriallibrary.xml
- Python Stubs: NX2412\ugopen\pythonStubs

Reason: Simcenter3D_2412 is a separate installation and should not be used.
NX2412 is the correct primary CAD/CAE environment.

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

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

docs/archive/NX_SOLVER_INTEGRATION.md

@@ -123,7 +123,7 @@ By default, NXSolver auto-detects NX installation:
 solver = NXSolver(nastran_version="2412")
 # Searches:
 # - C:/Program Files/Siemens/NX2412
-# - C:/Program Files/Siemens/Simcenter3D_2412
+# - C:/Program Files/Siemens/NX2412
 # - C:/Program Files (x86)/Siemens/NX2412
 ```