Add comprehensive test suite for image processing and related services

- Implement tests for database generator to ensure proper session handling.
- Create tests for EXIF extraction and conversion functions.
- Add tests for image-related endpoints, ensuring proper data retrieval and isolation between clients.
- Develop tests for OCR functionality, including language detection and text extraction.
- Introduce tests for the image processing pipeline, covering success and failure scenarios.
- Validate rate limiting functionality and ensure independent counters for different clients.
- Implement scraper tests to verify HTML content fetching and error handling.
- Add unit tests for various services, including storage and filename generation.
- Establish worker entry point for ARQ to handle background image processing tasks.

app/routers/files.py

@@ -0,0 +1,68 @@
+"""
+Router — Files : sert les fichiers locaux via URLs signées HMAC.
+
+Monté uniquement quand STORAGE_BACKEND == "local".
+"""
+import logging
+from pathlib import Path
+
+from fastapi import APIRouter, HTTPException, status
+from fastapi.responses import FileResponse
+
+from app.config import settings
+from app.services.storage_backend import get_storage_backend, LocalStorage
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/files", tags=["Fichiers"])
+
+
+@router.get(
+    "/signed/{token}",
+    summary="Télécharger un fichier via URL signée",
+    description="Valide le token HMAC et retourne le fichier correspondant.",
+)
+async def serve_signed_file(token: str):
+    """Sert un fichier local via un token HMAC signé."""
+    backend = get_storage_backend()
+
+    if not isinstance(backend, LocalStorage):
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="Endpoint non disponible avec le backend de stockage actuel",
+        )
+
+    # Valider le token
+    path = backend.validate_token(token)
+    if path is None:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Token invalide ou expiré",
+        )
+
+    # Vérifier que le fichier existe
+    abs_path = backend.get_absolute_path(path)
+    if not abs_path.exists():
+        raise HTTPException(
+            status_code=status.HTTP_410_GONE,
+            detail="Le fichier n'existe plus",
+        )
+
+    # Détecter le content type
+    suffix = abs_path.suffix.lower()
+    mime_map = {
+        ".jpg": "image/jpeg",
+        ".jpeg": "image/jpeg",
+        ".png": "image/png",
+        ".gif": "image/gif",
+        ".webp": "image/webp",
+        ".bmp": "image/bmp",
+        ".tiff": "image/tiff",
+    }
+    media_type = mime_map.get(suffix, "application/octet-stream")
+
+    return FileResponse(
+        path=str(abs_path),
+        media_type=media_type,
+        filename=abs_path.name,
+    )