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

* feat: add nix as option for RAG runner

* fix: remove default embedding model

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* stylua format

---------

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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

py/rag-service/shell.nix

@@ -0,0 +1,46 @@
+{ pkgs ? import <nixpkgs> {} }:
+let
+  logFile = "shell_log.txt";
+  python = pkgs.python311;
+in pkgs.mkShell {
+  packages = [
+    python
+    pkgs.uv
+    pkgs.stdenv.cc.cc.lib
+  ];
+  env = {
+    PYTHONUNBUFFERED = 1;
+    PYTHONDONTWRITEBYTECODE = 1;
+    LD_LIBRARY_PATH = "${pkgs.stdenv.cc.cc.lib}/lib:$LD_LIBRARY_PATH";
+  };
+  shellHook = ''
+
+    # Start with a fresh log file
+    echo "=== avante.nvim RAG service setup log $(date '+%Y-%m-%d %H:%M:%S') ===" > "${logFile}"
+
+    # Function to run commands and log their output
+    run_and_log() {
+      echo "$ $1" >> "${logFile}"
+      eval "$1" 2>&1 | tee -a "${logFile}"
+      echo "" >> "${logFile}"
+    }
+
+    # Log environment info
+    run_and_log "echo 'Environment: $(uname -a)'"
+    run_and_log "echo 'Python version: $(python --version)'"
+    run_and_log "echo 'UV version: $(uv --version)'"
+
+
+    if [ ! -d ".venv" ]; then
+      run_and_log "uv venv"
+    else
+      echo "Using existing virtual environment"  tee -a "${logFile}"
+    fi
+
+    run_and_log source ".venv/bin/activate"
+
+    run_and_log "uv pip install -r requirements.txt"
+
+    run_and_log "uv run fastapi run src/main.py --port $PORT --workers 3"
+    '';
+}