fix(ci): JDK 21 설치 — Adoptium Temurin APT 저장소 사용

node:24(Debian bookworm) 기본 apt에 openjdk-21 없음.
Adoptium GPG 키 + 저장소 추가 후 temurin-21-jdk 설치.

.gitea/workflows/deploy.yml

@@ -34,8 +34,14 @@ jobs:
       - name: Install JDK 21 + Maven
         run: |
           apt-get update -qq
-          apt-get install -y -qq openjdk-21-jdk-headless maven > /dev/null 2>&1
-          java -version
+          apt-get install -y -qq wget apt-transport-https gpg maven > /dev/null 2>&1
+          wget -qO - https://packages.adoptium.net/artifactory/api/gpg/key/public | gpg --dearmor -o /usr/share/keyrings/adoptium.gpg
+          echo "deb [signed-by=/usr/share/keyrings/adoptium.gpg] https://packages.adoptium.net/artifactory/deb bookworm main" > /etc/apt/sources.list.d/adoptium.list
+          apt-get update -qq
+          apt-get install -y -qq temurin-21-jdk > /dev/null 2>&1
+          echo "JAVA_HOME=/usr/lib/jvm/temurin-21-jdk-amd64" >> $GITHUB_ENV
+          echo "/usr/lib/jvm/temurin-21-jdk-amd64/bin" >> $GITHUB_PATH
+          /usr/lib/jvm/temurin-21-jdk-amd64/bin/java -version
           mvn --version
 
       - name: Build backend