Implement backtracking algorithms

Create implementations for common backtracking algorithm problems:

## Algorithms to implement:
- N-Queens problem
- Sudoku solver
- Permutations and combinations generator
- Subset sum problem
- Word search
- Hamiltonian path
- Graph coloring
- Knight's tour

## Requirements:
- Implement a general backtracking framework/template
- Provide detailed explanations of the backtracking approach
- Include visualization helpers where appropriate
- Document time and space complexity
- Create comprehensive test cases

## Educational value:
- Demonstrate pruning techniques to optimize backtracking
- Show state management in a functional programming context
- Highlight differences between exhaustive search and optimized backtracking

This will expand the algorithm collection to include important combinatorial search techniques.