Add CI that checks the function writes to Neo4j

[HarshCasper]

CI deployed the SAM app but never started Neo4j, never set the function's connection variables and never invoked the function, so it could not tell whether the sample works.

Test:

• New test.sh (make test) invokes the function with event.json plus a unique marker and checks:
  • the invocation succeeds and returns the Lambda account usage (FunctionCount, TotalCodeSize)
  • Neo4j has exactly one LambdaEvent node holding that event, queried with cypher-shell

Sample fixes:

• The Neo4j connection came from a manual update-function-configuration step after deploy. The template now sets NEO4J_URI, NEO4J_USERNAME and NEO4J_PASSWORD from parameters whose defaults match the compose setup, so make deploy produces a working function. The README shows --parameter-overrides for other databases.
• The neo4j 4.3.5 driver speaks a Bolt version current Neo4j no longer accepts. Moved to the neo4j 5.28 driver (execute_write replaces write_transaction) and pinned the database image to neo4j:5.26 instead of latest.
• Runtime python3.10 is past its deprecation date. Moved to python3.12, with jsonpickle 4.1 and aws-xray-sdk 2.15.
• make start and make stop used docker-compose, which current runners and Docker installs no longer ship. They use docker compose, and make start waits until LocalStack and Neo4j are ready. Dropped the obsolete compose version key and LOCALSTACK_API_KEY.

Workflow:

• Starts LocalStack and Neo4j with make start (Docker Compose, so the Lambda containers can resolve neo4j), then runs make deploy and make test, and prints the container logs on failure.
• Python 3.12, Node 22, permissions: contents: read, 20 minute timeout.

Verified by CI.

https://claude.ai/code/session_01DZfDmzUBPqNAu3yFKyfCNM