refactor: Major reorganization of optimization_engine module structure

BREAKING CHANGE: Module paths have been reorganized for better maintainability.
Backwards compatibility aliases with deprecation warnings are provided.

New Structure:
- core/           - Optimization runners (runner, intelligent_optimizer, etc.)
- processors/     - Data processing
  - surrogates/   - Neural network surrogates
- nx/             - NX/Nastran integration (solver, updater, session_manager)
- study/          - Study management (creator, wizard, state, reset)
- reporting/      - Reports and analysis (visualizer, report_generator)
- config/         - Configuration management (manager, builder)
- utils/          - Utilities (logger, auto_doc, etc.)
- future/         - Research/experimental code

Migration:
- ~200 import changes across 125 files
- All __init__.py files use lazy loading to avoid circular imports
- Backwards compatibility layer supports old import paths with warnings
- All existing functionality preserved

To migrate existing code:
  OLD: from optimization_engine.nx_solver import NXSolver
  NEW: from optimization_engine.nx.solver import NXSolver

  OLD: from optimization_engine.runner import OptimizationRunner
  NEW: from optimization_engine.core.runner import OptimizationRunner

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

optimization_engine/nx/__init__.py

@@ -0,0 +1,51 @@
+"""
+NX Integration
+==============
+
+Siemens NX and Nastran integration modules.
+
+Modules:
+- solver: NXSolver for running simulations
+- updater: NXParameterUpdater for design updates
+- session_manager: NX session lifecycle management
+- solve_simulation: Low-level simulation execution
+"""
+
+# Lazy imports to avoid import errors when NX modules aren't available
+def __getattr__(name):
+    if name == 'NXSolver':
+        from .solver import NXSolver
+        return NXSolver
+    elif name == 'run_nx_simulation':
+        from .solver import run_nx_simulation
+        return run_nx_simulation
+    elif name == 'NXParameterUpdater':
+        from .updater import NXParameterUpdater
+        return NXParameterUpdater
+    elif name == 'update_nx_model':
+        from .updater import update_nx_model
+        return update_nx_model
+    elif name == 'NXSessionManager':
+        from .session_manager import NXSessionManager
+        return NXSessionManager
+    elif name == 'NXSessionInfo':
+        from .session_manager import NXSessionInfo
+        return NXSessionInfo
+    elif name == 'ModelCleanup':
+        from .model_cleanup import ModelCleanup
+        return ModelCleanup
+    elif name == 'cleanup_substudy':
+        from .model_cleanup import cleanup_substudy
+        return cleanup_substudy
+    raise AttributeError(f"module 'optimization_engine.nx' has no attribute '{name}'")
+
+__all__ = [
+    'NXSolver',
+    'run_nx_simulation',
+    'NXParameterUpdater',
+    'update_nx_model',
+    'NXSessionManager',
+    'NXSessionInfo',
+    'ModelCleanup',
+    'cleanup_substudy',
+]