ci: 添加标准 GitHub Actions CI（JDK 8/17/21 矩阵，全版本分支触发）

Author: loong10k

.github/workflows/ci.yml

@@ -0,0 +1,54 @@
+# CI workflow for easy4j Spring Boot Starter
+#
+# Triggers:
+#   - push / pull_request on all version-line branches
+#   - manual workflow_dispatch
+#
+# JDK matrix by version line:
+#   - 2.3.x / 2.7.x : JDK 8
+#   - 3.0.x ~ 3.5.x : JDK 17
+#   - 4.0.x / 4.1.x : JDK 17 / 21
+#
+# Runs `mvn -B clean verify` with dependency convergence checks.
+name: CI
+
+on:
+  push:
+    branches: [2.3.x, 2.7.x, 3.0.x, 3.1.x, 3.2.x, 3.3.x, 3.4.x, 3.5.x, 4.0.x, 4.1.x, master, main]
+  pull_request:
+    branches: [2.3.x, 2.7.x, 3.0.x, 3.1.x, 3.2.x, 3.3.x, 3.4.x, 3.5.x, 4.0.x, 4.1.x, master, main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: JDK ${{ matrix.java }} Build & Verify
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        java: [8, 17, 21]
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v4
+
+      - name: Set up JDK ${{ matrix.java }}
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: ${{ matrix.java }}
+          cache: maven
+
+      - name: Build and verify
+        run: mvn -B --no-transfer-progress clean verify
+
+      - name: Upload surefire reports
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: surefire-reports-jdk${{ matrix.java }}
+          path: target/surefire-reports
+          retention-days: 14