feat: PaddleOCR Remote-Engine (PP-OCRv5 Latin auf Hetzner x86_64)

PaddleOCR als neue engine=paddle Option in der OCR-Pipeline.
Microservice auf Hetzner (paddleocr-service/), async HTTP-Client
(paddleocr_remote.py), Frontend-Dropdown, automatisch words_first.

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

klausur-service/backend/services/paddleocr_remote.py

@@ -0,0 +1,44 @@
+"""Remote PaddleOCR client — calls Hetzner service."""
+
+import logging
+import os
+from typing import Dict, List, Tuple
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+PADDLEOCR_REMOTE_URL = os.environ.get("PADDLEOCR_REMOTE_URL", "")
+PADDLEOCR_API_KEY = os.environ.get("PADDLEOCR_API_KEY", "")
+_TIMEOUT = 30.0
+
+
+async def ocr_remote_paddle(
+    image_bytes: bytes,
+    filename: str = "scan.png",
+) -> Tuple[List[Dict], int, int]:
+    """Send image to remote PaddleOCR, return (word_dicts, img_w, img_h)."""
+    if not PADDLEOCR_REMOTE_URL:
+        raise RuntimeError("PADDLEOCR_REMOTE_URL not configured")
+
+    headers = {}
+    if PADDLEOCR_API_KEY:
+        headers["X-API-Key"] = PADDLEOCR_API_KEY
+
+    async with httpx.AsyncClient(timeout=_TIMEOUT, verify=False) as client:
+        resp = await client.post(
+            f"{PADDLEOCR_REMOTE_URL.rstrip('/')}/ocr",
+            files={"file": (filename, image_bytes, "image/png")},
+            headers=headers,
+        )
+        resp.raise_for_status()
+        data = resp.json()
+
+    words = data.get("words", [])
+    logger.info(
+        "PaddleOCR remote returned %d words (img %dx%d)",
+        len(words),
+        data.get("image_width", 0),
+        data.get("image_height", 0),
+    )
+    return words, data["image_width"], data["image_height"]