fix(6): correct venv path in start_server.sh - create in project root

- Virtual environment should be .venv in project root, not parent folder
- Fix venv creation and activation path logic
- Ensures venv is created and found in correct location

start_server.sh

@@ -104,15 +104,17 @@ if [[ ! -f "requirements.txt" ]]; then
   log_error "backend/requirements.txt not found"
 fi
 
-# Create and use Python virtual environment
-VENV_DIR="../.venv"
+# Create and use Python virtual environment in project root
+VENV_DIR=".venv"
 if [[ ! -d "$VENV_DIR" ]]; then
   log_info "  Creating Python virtual environment..."
+  cd - > /dev/null || true  # Return to project root
   python3 -m venv "$VENV_DIR" || log_error "Failed to create virtual environment"
+  cd backend || log_error "Failed to enter backend directory"
 fi
 
-# Activate virtual environment
-source "$VENV_DIR/bin/activate"
+# Activate virtual environment (from project root)
+source "../$VENV_DIR/bin/activate"
 
 # Install dependencies if needed
 if ! python3 -c "import fastapi" &> /dev/null; then