Fix Docker Compose version warning and improve script permissions

DOCKER COMPOSE:
- Removed obsolete 'version' attribute from docker-compose.yml
- Keeps db-ui image as ghcr.io/n7olkachev/db-ui:latest

SCRIPT PERMISSIONS:
- Updated README.md with recursive chmod command: find . -name '*.sh' -exec chmod +x {} \;
- Updated QUICKSTART.md with Step 0: Make Scripts Executable
- Removed individual chmod commands from each step
- Single command makes all .sh files executable at once

DOCUMENTATION:
- Renumbered steps in QUICKSTART.md for clarity
- Step 0: Make Scripts Executable
- Step 1: Install Dependencies (Optional)
- Step 2: Start Docker Containers
- Step 3: Initialize Database Schema
- Step 4: Generate Test Data

This resolves the Docker Compose warning and simplifies the setup process with a single chmod command.

docker-compose.yml

@@ -1,5 +1,3 @@
-version: '3.8'
-
 services:
   postgres:
     image: postgres:16-alpine