services/search/cache.py set CACHE_DIR = services/cache (the source tree) and
mkdir'd it at import, unguarded. In Docker services/ is the read-only image
layer, so the mkdir fails at import (same class as the analytics bug #2366).
Move the cache under DATA_DIR/cache (writable on Docker and native) and wrap
the mkdir so an unwritable path disables disk cache instead of crashing import.
Part of #3331.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Kenny Van de Maele