feat: add Nix as Rag service runner option (#1480)

* feat: add nix as option for RAG runner

* fix: remove default embedding model

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* stylua format

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

py/rag-service/run.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+# Set the target directory (use the first argument or default to a temporary directory)
+TARGET_DIR=$1
+if [ -z "$TARGET_DIR" ]; then
+  TARGET_DIR="/tmp/avante-rag-service"
+fi
+# Create the target directory if it doesn't exist
+mkdir -p "$TARGET_DIR"
+
+# Copy the required files to the target directory
+cp -r src/ "$TARGET_DIR"
+cp requirements.txt "$TARGET_DIR"
+cp shell.nix "$TARGET_DIR"
+
+echo "Files have been copied to $TARGET_DIR"
+
+# Change to the target directory
+cd "$TARGET_DIR"
+
+# Run the RAG service using nix-shell
+# The environment variables (PORT, DATA_DIR, OPENAI_API_KEY, OPENAI_BASE_URL) are passed from the parent process
+nix-shell