feat: issue/0020 — generacion de PDFs en Python y Go

Añade 3 tipos Python (PDFDoc, PDFPage, PDFStyle) y 10 funciones Python
para construir PDFs con fpdf2 (builder fluent), fusionar PDFs con pypdf
y convertir HTML/Markdown a PDF via weasyprint (stub si no disponible).
Añade pdf_simple_report en Go como stub hasta que go-pdf/fpdf se integre.

- python/types/infra/: pdf_doc, pdf_page, pdf_style
- python/functions/infra/: pdf_create, pdf_add_page, pdf_add_text,
  pdf_add_table, pdf_add_image, pdf_add_header_footer, pdf_from_html,
  pdf_from_markdown, pdf_merge, pdf_save
- functions/infra/pdf_simple_report.go: stub Go con ReportSection/ReportTable
- 17 tests Python pasando (pytest)
- fpdf2 y pypdf añadidos via uv al venv Python

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

python/functions/infra/pdf_add_text_test.py

@@ -0,0 +1,42 @@
+"""Tests para pdf_add_text."""
+
+import sys
+import os
+
+sys.path.insert(0, os.path.dirname(__file__))
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), "..", "..", "..", "python", "types", "infra"))
+
+from pdf_create import pdf_create
+from pdf_add_page import pdf_add_page
+from pdf_add_text import pdf_add_text
+from pdf_save import pdf_save
+from pdf_doc import PDFDoc
+from pdf_style import PDFStyle
+
+
+def test_texto_simple_con_estilo_defecto():
+    doc = pdf_create(title="Test")
+    doc = pdf_add_page(doc)
+    doc = pdf_add_text(doc, "Hola mundo")
+    assert isinstance(doc, PDFDoc)
+    # El PDF debe ser valido
+    pdf_bytes = pdf_save(doc)
+    assert pdf_bytes[:4] == b"%PDF"
+
+
+def test_texto_con_estilo_personalizado_bold_centrado():
+    doc = pdf_create()
+    doc = pdf_add_page(doc)
+    style = PDFStyle(font_family="Helvetica-Bold", font_size=18.0, alignment="center", color="#FF0000")
+    doc = pdf_add_text(doc, "Titulo en Rojo", style=style)
+    pdf_bytes = pdf_save(doc)
+    assert pdf_bytes[:4] == b"%PDF"
+
+
+def test_texto_multilinea_con_saltos():
+    doc = pdf_create()
+    doc = pdf_add_page(doc)
+    doc = pdf_add_text(doc, "Linea 1\nLinea 2\nLinea 3")
+    pdf_bytes = pdf_save(doc)
+    assert pdf_bytes[:4] == b"%PDF"
+    assert len(pdf_bytes) > 100