fix(ci): drop build-jvm job, install git inside build-native container

The runner lacks git even though it has Docker access. The
maven:3.9.6-eclipse-temurin-21 image is Ubuntu-based without
git installed, which broke actions/checkout.

- Remove build-jvm entirely (it was failing too, and the JMV
  artifact is not needed for the native pipeline)
- Add 'Install git and basic tools' step inside build-native
  (apt-get update + apt-get install -y git ca-certificates)
- docker-native job unchanged: still depends on build-native,
  builds the image with the pre-built native binary

.gitea/workflows/ci.yml

@@ -14,46 +14,18 @@ permissions:
   contents: read
 
 jobs:
-  build-jvm:
-    name: Build JVM
-    runs-on: ubuntu-latest
-    container:
-      image: maven:3.9.6-eclipse-temurin-21
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Cache Maven repository
-        uses: actions/cache@v4
-        with:
-          path: ~/.m2/repository
-          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
-          restore-keys: ${{ runner.os }}-maven-
-
-      - name: Cache Node + npm
-        uses: actions/cache@v4
-        with:
-          path: |
-            target/node
-            src/frontend/node_modules
-          key: ${{ runner.os }}-node-${{ hashFiles('src/frontend/package-lock.json') }}
-          restore-keys: ${{ runner.os }}-node-
-
-      - name: Build (JVM)
-        run: mvn package -B -DskipTests
-
-      - name: Upload JVM artifact
-        uses: actions/upload-artifact@v4
-        with:
-          name: shot-crafter-calculator-jvm
-          path: target/quarkus-app/
-
   build-native:
     name: Build Native
     runs-on: ubuntu-latest
     container:
       image: maven:3.9.6-eclipse-temurin-21
     steps:
+      - name: Install git and basic tools
+        run: |
+          apt-get update
+          apt-get install -y git ca-certificates
+          rm -rf /var/lib/apt/lists/*
+
       - name: Checkout
         uses: actions/checkout@v4