Add automated data profiling and exploratory analysis

[gelluisaac]

Description

    Build automated data profiling tools that generate comprehensive exploratory data analysis reports with statistics, visualizations, and insights.

    ## Files to modify
    - astroml/preprocessing/profiling/data_profiler.py
    - astroml/preprocessing/profiling/report_generator.py
    - astroml/preprocessing/profiling/visualizations.py
    - astroml/api/routers/data_profiling.py
    - astroml/preprocessing/profiling/insights.py

    ## Out of scope
    - Refactoring unrelated modules
    - Changing public API contracts
    - Major version bumps or breaking changes
    - Performance optimizations not directly related to the issue

    ## Acceptance criteria
    - [ ] Code changes implemented as per procedure steps
    - [ ] All new code has complete type hints
    - [ ] Unit tests added/updated with >90% coverage for changed code
    - [ ] All tests pass: pytest tests/
    - [ ] Linting passes: pre-commit run --all-files
    - [ ] Documentation updated if needed
    - [ ] Changes reviewed and approved

    ## Procedure
    1. Implement statistical profiling (mean, median, distributions)
    2. Build correlation analysis and heatmaps
    3. Add missing value analysis
    4. Implement outlier detection in profiling
    5. Create automated report generation (HTML/PDF)
    6. Add data quality scoring
    7. Implement profiling API
    8. Test with various dataset types