Remove duplicate/unnecessary code after proper analysis

REMOVED (Duplicate Code):
- backend/src/ - DUPLICATE of src/ (same files in both locations)
- backend/santok/ - DUPLICATE of santok/ package
- backend/setup.py - Duplicate setup file
- backend/demo_complete_workflow.py - Demo file, not production
- backend/run_all_python.py - Utility script, not production

REMOVED (Development Utilities):
- collect_python_files.py - Dev utility (not production code)
- create_santok_zip.py - Dev utility (not production code)
- package_backend.py - Dev utility (not production code)
- run_all_python.py - Dev utility (not production code)
- verify_installation.py - Dev utility (not production code)

REMOVED (Temporary Files):
- examples/tmp*.py - Temporary Python files

KEPT (Essential Production Code):
- santok/ - Core package (used by run.py, start.py, setup.py)
- src/ - Main source code (used by main.py, santok_cli.py, train_santok_complete.py)
- enhanced_semantic_trainer/ - Used by santok_cli.py
- examples/ - User examples (helpful for users)
- All entry points (main.py, run.py, start.py, santok_cli.py, train_santok_complete.py)
- setup.py, README.md, requirements.txt

Author: chavalasantosh