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>

app/routers/convert.py

@@ -0,0 +1,78 @@
+"""Synchronous conversion.
+
+Suitable for smaller documents. Anything that does not finish within
+SYNC_TIMEOUT_SECONDS is cancelled and the caller is pointed at /jobs.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+
+from fastapi import APIRouter, Response
+from fastapi.responses import FileResponse
+from starlette.background import BackgroundTask
+
+from ..deps import get_container
+from ..errors import ConversionError, SyncTooLongError, error_from_code
+from ..models import ConvertRequest
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(tags=["konverze"])
+
+
+@router.post(
+    "/convert",
+    summary="Synchronni prevod HTML na PDF",
+    response_class=Response,
+    responses={
+        200: {"content": {"application/pdf": {}}, "description": "Hotove PDF."},
+        413: {"description": "Konverze trvala dele nez limit, pouzijte POST /jobs."},
+    },
+)
+async def convert(request: ConvertRequest):
+    container = get_container()
+    settings = container.settings
+    manager = container.jobs
+
+    job = manager.submit(request)
+
+    try:
+        await asyncio.wait_for(job.done.wait(), timeout=settings.sync_timeout_seconds)
+    except asyncio.TimeoutError as exc:
+        manager.cancel(job.id)
+        logger.warning(
+            "Synchronous conversion exceeded its budget",
+            extra={"job_id": job.id, "limit_seconds": settings.sync_timeout_seconds},
+        )
+        raise SyncTooLongError(
+            "Konverze presahla limit pro synchronni pozadavek. Pouzijte asynchronni endpoint POST /jobs.",
+            {"limit_seconds": settings.sync_timeout_seconds},
+        ) from exc
+
+    if job.state.status != "done":
+        error = job.state.error
+        if error is not None:
+            raise error_from_code(error.error_code, error.message, error.detail)
+        raise ConversionError("Konverze skoncila ve stavu " + job.state.status + ".")
+
+    path = container.storage.result_path(job.id)
+    filename = request.filename or "dokument.pdf"
+
+    headers = {
+        "X-Page-Count": str(job.state.page_count or 0),
+        "X-Engine-Used": job.state.engine_used or "",
+    }
+    if job.state.missing_assets:
+        headers["X-Missing-Assets"] = str(len(job.state.missing_assets))
+    if job.state.warnings:
+        headers["X-Warnings"] = str(len(job.state.warnings))
+
+    return FileResponse(
+        path,
+        media_type="application/pdf",
+        filename=filename,
+        headers=headers,
+        background=BackgroundTask(container.storage.discard, job.id),
+    )