Implementace prevodu HTML na PDF

Sluzba prijme adresu HTML dokumentu nebo HTML v tele requestu a vrati PDF.
Navrzena pro dokumenty o stovkach az tisicich stranek.

Rendering:
- WeasyPrint jako vychozi engine, spravne CSS Paged Media, nizka pametova
  narocnost, bez JavaScriptu
- Chromium pres Playwright pro dokumenty dokreslovane skripty
- rezim auto s detekci skriptu a fallbackem pri selhani WeasyPrintu

Velke dokumenty:
- deleni na casti na strukturalnich hranicich, rez nikdy uvnitr tabulky
  nebo odstavce
- dvoupruchodovy render obsahu se skutecnymi cisly stranek, pozice nadpisu
  se ctou z kotev hlasenych u kazde stranky
- cislovani stranek bud pres CSS countery, nebo pres cislovaci vrstvu
  nastampovanou na hotove PDF, rozmer stranky se cte z vysledneho souboru
- Chromium se restartuje po N jobech, nikdy vsak behem beziciho renderu

API:
- POST /convert synchronne, POST /jobs asynchronne se sledovanim stavu,
  stahovanim vysledku, rusenim a volitelnym callbackem
- GET /health s overenim dostupnosti obou enginu a stavem fronty
- OpenAPI respektuje prefix reverse proxy pres root_path

Bezpecnost a provoz:
- SSRF kontrola po DNS resolvu, na kazdem presmerovani a u vsech pozadavku
  prohlizece
- nedostupne assety render nezastavi, ale hlasi se v odpovedi i v logu
- fronta s omezenym poctem workeru, rozpracovane joby se pri ukonceni
  oznaci jako failed, nezmizi potichu
- strukturovane JSON logovani s job_id
- vsechny limity vypnute ve vychozim stavu

Dockerfile je dvoufazovy, obsahuje zavislosti WeasyPrintu, Chromium
a fonty s ceskou diakritikou.

Autentizace zamerne neni implementovana, zpusob predavani neni domluveny.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/test_chunker.py

@@ -0,0 +1,56 @@
+"""Splitting of the document into chunks."""
+
+from __future__ import annotations
+
+from app.pdf.chunker import split_document
+from app.pdf.document import SourceDocument
+from tests.conftest import build_document
+
+
+def test_document_with_sections_is_split() -> None:
+    document = SourceDocument(build_document(sections=40, paragraphs_per_section=10))
+    chunks = split_document(document, pages_per_chunk=5)
+
+    assert len(chunks) > 1
+    for chunk in chunks:
+        assert chunk.startswith("<!DOCTYPE html>")
+        assert "<body" in chunk
+        assert "</html>" in chunk
+
+
+def test_every_section_appears_exactly_once() -> None:
+    document = SourceDocument(build_document(sections=30, paragraphs_per_section=8))
+    chunks = split_document(document, pages_per_chunk=3)
+
+    joined = "".join(chunks)
+    for index in range(30):
+        assert joined.count(f"id=\"sekce-{index}\"") == 1
+
+
+def test_head_is_repeated_in_every_chunk() -> None:
+    document = SourceDocument(build_document(sections=20, paragraphs_per_section=10))
+    chunks = split_document(document, pages_per_chunk=2)
+
+    assert len(chunks) > 1
+    for chunk in chunks:
+        assert "font-family:sans-serif" in chunk
+
+
+def test_document_without_split_points_stays_whole(unsplittable_document: str) -> None:
+    document = SourceDocument(unsplittable_document)
+    chunks = split_document(document, pages_per_chunk=1)
+
+    assert len(chunks) == 1
+
+
+def test_single_wrapper_is_traversed() -> None:
+    sections = "".join(f"<section><h1>Kapitola {i}</h1><p>Text</p></section>" for i in range(10))
+    html = f"<!DOCTYPE html><html><head></head><body><main class='obal'>{sections}</main></body></html>"
+
+    document = SourceDocument(html)
+    assert document.container.tag == "main"
+
+    chunks = split_document(document, pages_per_chunk=1)
+    assert len(chunks) > 1
+    for chunk in chunks:
+        assert "class=\"obal\"" in chunk