fix(ci): add verify step before upload to debug missing binary

The upload-artifact step failed with exit code 1 but no details.
The most likely cause is that the binary file does not exist
at the expected path `target/shot-crafter-calculator-1.0.0-runner`
because the native build may have failed silently.

Add a 'Verify native binary' step that runs `ls -la target/` and
`file target/shot-crafter-calculator-1.0.0-runner` so the next
log shows exactly what's in target/ and what type the runtime
sees the binary as. Also make the upload's 'if-no-files-found'
explicit so the failure mode is unambiguous.

.gitea/workflows/ci.yml

@@ -61,11 +61,17 @@ jobs:
       - name: Build (Native)
         run: mvn package -Pnative -B -DskipTests -Dquarkus.native.native-image-xmx=4g
 
+      - name: Verify native binary
+        run: |
+          ls -la target/
+          file target/shot-crafter-calculator-1.0.0-runner 2>/dev/null || echo "binary not found"
+
       - name: Upload Native binary
         uses: actions/upload-artifact@v4
         with:
           name: shot-crafter-calculator-runner
           path: target/shot-crafter-calculator-1.0.0-runner
+          if-no-files-found: error
 
   docker-native:
     name: Build & Push Native Image