feat(eda): render de models en markdown + PDF DB-level para profile_database (H4,H9)

- H4: render_eda_markdown anade seccion Modelos (PCA/KMeans/normalidad/outliers);
  render_eda_pdf formatea models/series/caveats como tablas (no str(dict) crudo)
- H9: profile_database gana flag emit_pdf -> PDF movil DB-level (resumen tablas +
  join graph) via render_eda_pdf_relational; clave report_pdf_path
- aditivos y retrocompatibles (flags default False). 38 tests verdes

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

python/functions/datascience/__init__.py

@@ -52,7 +52,7 @@ from .to_returns import to_returns
 from .fdr_correction import fdr_correction
 from .suggest_reexpression import suggest_reexpression
 from .exploratory_caveats import exploratory_caveats
-from .render_eda_pdf import render_eda_pdf
+from .render_eda_pdf import render_eda_pdf, render_eda_pdf_relational
 
 __all__ = [
     "decode_qr_image",
@@ -64,6 +64,7 @@ __all__ = [
     "suggest_reexpression",
     "exploratory_caveats",
     "render_eda_pdf",
+    "render_eda_pdf_relational",
     "summarize_table_duckdb",
     "summarize_table_pg",
     "spearman_corr",