Fix JitPack version resolution issue

- Replace Maven property placeholders with actual version before build
- JitPack doesn't resolve ${dynamodb-toolkit.version} expressions
- Use sed to substitute $VERSION from JitPack into both pom.xml files

Author: wassertim

jitpack.yml

@@ -1,4 +1,7 @@
 jdk:
   - openjdk21
+before_install:
+  - sed -i "s/\${dynamodb-toolkit.version}/$VERSION/g" pom.xml
+  - sed -i "s/\${dynamodb-toolkit.version}/$VERSION/g" integration-tests/pom.xml
 install:
   - mvn clean compile -DskipTests=true