fix(files): un Maker non cancella statistics/reports/logo, GET ristretto (#21)

DELETE /api/files/{path} non aveva nessun legame con ricetta/proprietario:
un Maker poteva cancellare qualunque file sotto uploads, compresi i CSV di
statistica di produzioni altrui. Ora: statistics/, reports/, logos/ sono
403 sempre (il logo si cambia da PUT /api/settings/logo); un file di
ricetta (task.file_path, subtask.image_path, recipe.image_path) e' 409 se
referenziato da una versione non corrente o che ha gia' misurazioni - un
file non referenziato resta cancellabile. GET di statistics/* e reports/*
richiede Metrologist, Supervisor o admin (prima bastava essere autenticati).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/backend/api/routers/files.py

@@ -6,9 +6,15 @@ from pathlib import Path
 from fastapi import APIRouter, Depends, File, HTTPException, UploadFile, status
 from fastapi.responses import FileResponse
 from PIL import Image
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.backend.config import settings
+from src.backend.database import get_db
 from src.backend.api.middleware.api_key import get_current_user, require_maker
+from src.backend.models.orm.measurement import Measurement
+from src.backend.models.orm.recipe import Recipe, RecipeVersion
+from src.backend.models.orm.task import RecipeSubtask, RecipeTask
 from src.backend.models.orm.user import User
 
 logger = logging.getLogger(__name__)
@@ -20,6 +26,59 @@ ALLOWED_IMAGE_TYPES = {"image/jpeg", "image/png", "image/gif", "image/webp"}
 ALLOWED_PDF_TYPE = "application/pdf"
 ALLOWED_TYPES = ALLOWED_IMAGE_TYPES | {ALLOWED_PDF_TYPE}
 
+# Top-level folders nothing may DELETE through this router: statistics/reports are
+# audit records, the logo is only ever replaced via POST /api/settings/logo.
+_UNDELETABLE_PREFIXES = ("statistics/", "reports/", "logos/")
+
+# GET under these needs a role that is meant to see production data, not just
+# any authenticated user (a Maker or MeasurementTec has no business reading
+# every production's statistics/report file by guessing its name).
+_RESTRICTED_GET_PREFIXES = ("statistics/", "reports/")
+
+
+def _can_read_restricted(user: User) -> bool:
+    return user.is_admin or user.has_role("Metrologist") or user.has_role("Supervisor")
+
+
+async def _is_recipe_file_protected(db: AsyncSession, relative_path: str) -> bool:
+    """True when `relative_path` (uploads-relative, forward slashes) must not be
+    deleted: it is a recipe's cover image, or a task/subtask file belonging to a
+    version that is either not the current one (kept for history) or already has
+    measurements against it (the audit trail needs it to make sense of them).
+
+    A path not referenced anywhere is safe to delete (orphaned upload).
+    """
+    recipe_hit = (await db.execute(
+        select(Recipe.id).where(Recipe.image_path == relative_path)
+    )).scalar_one_or_none()
+    if recipe_hit is not None:
+        return True
+
+    version_id = (await db.execute(
+        select(RecipeTask.version_id).where(RecipeTask.file_path == relative_path)
+    )).scalar_one_or_none()
+
+    if version_id is None:
+        version_id = (await db.execute(
+            select(RecipeTask.version_id)
+            .join(RecipeSubtask, RecipeSubtask.task_id == RecipeTask.id)
+            .where(RecipeSubtask.image_path == relative_path)
+        )).scalar_one_or_none()
+
+    if version_id is None:
+        return False
+
+    version = (await db.execute(
+        select(RecipeVersion).where(RecipeVersion.id == version_id)
+    )).scalar_one_or_none()
+    if version is None or not version.is_current:
+        return True
+
+    has_measurements = (await db.execute(
+        select(Measurement.id).where(Measurement.version_id == version_id).limit(1)
+    )).scalar_one_or_none() is not None
+    return has_measurements
+
 
 def validate_file_type(content_type: str) -> bool:
     """Validate if file type is allowed."""
@@ -195,8 +254,14 @@ async def get_file(
 ):
     """Serve a file from the uploads directory.
 
-    Requires authentication but no specific role.
+    Requires authentication; statistics/ and reports/ additionally require
+    Metrologist, Supervisor or admin, since those are production data.
     """
+    if file_path.startswith(_RESTRICTED_GET_PREFIXES) and not _can_read_restricted(user):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="Metrologist, Supervisor or admin role required",
+        )
     full_path = resolve_upload_path(file_path)
     return FileResponse(full_path)
 
@@ -205,13 +270,29 @@ async def get_file(
 async def delete_file(
     file_path: str,
     user: User = Depends(require_maker),
+    db: AsyncSession = Depends(get_db),
 ):
     """Delete a file from the uploads directory.
 
-    Also deletes associated thumbnail if it exists.
+    Also deletes associated thumbnail if it exists. statistics/, reports/ and
+    logos/ can never be deleted here (403); a recipe file still referenced by
+    its current version or by a version with measurements is kept (409).
     """
+    if file_path.startswith(_UNDELETABLE_PREFIXES):
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail="This folder cannot be deleted through the files API.",
+        )
+
     full_path = resolve_upload_path(file_path)
 
+    relative_path = str(full_path.relative_to(settings.upload_path)).replace("\\", "/")
+    if await _is_recipe_file_protected(db, relative_path):
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="File is referenced by a current or measured recipe version.",
+        )
+
     # Delete thumbnail if it exists
     if full_path.parent.name != "thumbnails":
         thumbnail_path = full_path.parent / "thumbnails" / full_path.name