Hierarchical Level Support

Parent Epic: #155

# Task: Hierarchical Level Support

## Description
Enable variable n_levels parameter, refactoring the fixed 2-level assumption and supporting n_levels=1 for standard factor analysis mode.

## Acceptance Criteria
- [ ] n_levels parameter controls hierarchy depth
- [ ] n_levels=1 works as standard factor analysis
- [ ] n_levels>2 creates deeper hierarchies
- [ ] Data compatibility validated for levels
- [ ] Factor matching works across all levels

## Technical Details
- Refactor hierarchical loops in htfa/core/htfa.py
- Make hierarchy building dynamic based on n_levels
- Special case n_levels=1 to skip hierarchical optimization
- Validate data dimensions support requested levels
- Update factor matching algorithm

## Dependencies
- [ ] Tasks 164, 157, 158 must be complete

## Effort Estimate
- Size: M
- Hours: 8-10
- Parallel: false

## Definition of Done
- [ ] Variable levels implemented
- [ ] n_levels=1 mode works
- [ ] Tests for different levels
- [ ] Validation logic added
- [ ] Documentation updated