fix: code review — security fixes, dedup, cleanup

- setup: validate roles against users.VALID_ROLES (Supervisor was missing)
- files: fix path traversal prefix-match edge case (is_relative_to),
  dedupe path validation into resolve_upload_path(), use logging not print
- measurements: extract shared _build_measurement_filters() helper
- client app: prevent open redirect via Referer on /set-language
- maker: guard resp.json() in parse-technical-sheet proxy
- measure/maker: extract shared file proxy into services/file_proxy.py
- measure: localize supervisor validation error messages
- annotation-editor: remove global keydown listener in destroy()

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

src/frontend/flask_app/blueprints/maker.py

@@ -1,12 +1,13 @@
 """Maker blueprint - recipe creation and editing."""
 import requests as http_requests
 
-from flask import Blueprint, Response, flash, jsonify, redirect, render_template, request, session, url_for
+from flask import Blueprint, flash, jsonify, redirect, render_template, request, session, url_for
 from flask_babel import gettext as _
 
 from blueprints.auth import login_required, role_required
 from config import Config
 from services.api_client import api_client
+from services.file_proxy import proxy_file
 
 maker_bp = Blueprint("maker", __name__, url_prefix="/maker")
 
@@ -380,19 +381,7 @@ def api_upload_file():
 @login_required
 def api_get_file(file_path: str):
     """Proxy: Serve file from API server (browser can't send X-API-Key)."""
-    api_key = session.get("api_key", "")
-    base_url = Config.API_SERVER_URL.rstrip("/")
-    resp = http_requests.get(
-        f"{base_url}/api/files/{file_path}",
-        headers={"X-API-Key": api_key},
-        timeout=30,
-    )
-    if resp.status_code != 200:
-        return Response(resp.text, status=resp.status_code)
-    return Response(
-        resp.content,
-        content_type=resp.headers.get("content-type", "application/octet-stream"),
-    )
+    return proxy_file(file_path)
 
 
 @maker_bp.route("/api/files/<path:file_path>", methods=["DELETE"])
@@ -444,4 +433,11 @@ def api_parse_technical_sheet(recipe_id: int):
         timeout=90,
     )
 
-    return jsonify(resp.json()), resp.status_code
+    try:
+        payload = resp.json()
+    except ValueError:
+        payload = {
+            "error": True,
+            "detail": resp.text or f"HTTP {resp.status_code}",
+        }
+    return jsonify(payload), resp.status_code