[enh] container: build with uv (#5199)

This commit replaces `pip` in container builds with `uv` pip compat
with a 1:1 parity. The only thing that changes is the installation speed of the
wheels, which seems to be considerably faster, although I haven't been able to
properly quantify this yet.

uv also gives us more tools to manage the cache. We can revert the prior cache
changes in `container.yml` as we won't have duplicated wheels anymore.

utils/lib_sxng_container.sh

@@ -102,7 +102,8 @@ container.build() {
 
         # shellcheck disable=SC2086
         "$container_engine" $params_build_builder \
-            --build-arg="TIMESTAMP_SETTINGS=$(git log -1 --format="%cd" --date=unix -- ./searx/settings.yml)" \
+            --build-arg="TIMESTAMP=$(git log -1 --date=format:'%Y%m%d%H%M.%S' --format='%ad')" \
+            --build-arg="TIMESTAMP_SETTINGS=$(git log -1 --date=format:'%Y%m%d%H%M.%S' --format='%ad' ./searx/settings.yml)" \
             --tag="localhost/$CONTAINER_IMAGE_ORGANIZATION/$CONTAINER_IMAGE_NAME:builder" \
             --file="./container/builder.dockerfile" \
             .