Fix SearXNG editable install: use --no-build-isolation

SearXNG's build backend imports msgspec at metadata time; with build
isolation the preinstalled build deps were invisible, causing
ModuleNotFoundError: No module named 'msgspec'. Install with
--no-build-isolation so the venv's build deps are used.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Dockerfile

@@ -26,7 +26,7 @@ ARG SEARXNG_REF=master
 RUN git clone --depth 1 --branch "$SEARXNG_REF" https://github.com/searxng/searxng.git /usr/local/searxng
 RUN python -m venv /opt/searxng-venv \
     && /opt/searxng-venv/bin/pip install -U pip setuptools wheel pyyaml msgspec typing-extensions pybind11 \
-    && /opt/searxng-venv/bin/pip install --use-pep517 -e /usr/local/searxng
+    && /opt/searxng-venv/bin/pip install --use-pep517 --no-build-isolation -e /usr/local/searxng
 
 # --- Gradio app into its own venv ---
 RUN python -m venv /opt/appenv