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_large_document.py

@@ -0,0 +1,39 @@
+"""Measurement fixture for a document of roughly twelve hundred pages.
+
+Marked slow on purpose. It is here to measure memory and wall clock time of the
+chunked pipeline, not to assert exact numbers.
+"""
+
+from __future__ import annotations
+
+import time
+
+import pytest
+
+pytest.importorskip("weasyprint")
+
+from app.config import Settings  # noqa: E402
+from app.engines.weasy import WeasyPrintEngine  # noqa: E402
+from app.models import ChunkSettings, ConvertRequest, PageNumbers, Source  # noqa: E402
+from app.services.pipeline import ConversionPipeline  # noqa: E402
+
+pytestmark = [pytest.mark.asyncio, pytest.mark.slow]
+
+
+async def test_large_document_renders_in_chunks(tmp_path, large_document: str) -> None:
+    pipeline = ConversionPipeline({"weasyprint": WeasyPrintEngine()}, Settings())
+    request = ConvertRequest(
+        source=Source(html=large_document),
+        engine="weasyprint",
+        page_numbers=PageNumbers(enabled=True),
+        chunking=ChunkSettings(enabled=True, pages_per_chunk=50),
+    )
+
+    started = time.monotonic()
+    result = await pipeline.run(request, tmp_path)
+    duration = time.monotonic() - started
+
+    print(f"stranek: {result.page_count}, cas: {duration:.1f} s")
+
+    assert result.page_count > 1000
+    assert result.path.exists()