Add minimal runnable Spring Cloud Config demo

[Copilot]

The repository contained only raw config property files in respo/ with no runnable Spring project. This adds a two-module Maven project demonstrating Spring Cloud Config end-to-end.

Modules

• config-server (port 8888): @EnableConfigServer app backed by this repo's respo/ directory via local Git URI
• config-client (port 8080): Spring Boot REST app that imports config from the server at startup, exposing two endpoints driven by values in respo/config-client-dev.properties

Endpoints

GET /foo      → "foo version 5"
GET /message  → "hello spring io"

Project structure

pom.xml                          ← parent (Spring Boot 2.7.18, Spring Cloud 2021.0.8)
config-server/                   ← Config Server module
config-client/                   ← Config Client module
respo/                           ← existing git-backed config files (unchanged)

Config client uses spring.config.import=optional:configserver:http://localhost:8888 (Spring Cloud 2021+ style, no bootstrap context needed).

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[wanggghere]

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