feat(java): add a read-only Neo4j analysis backend (parity with Python/TypeScript) #167

Summary

Add a read-only Neo4j-backed Java analysis backend (cldk.analysis.java.neo4j.JNeo4jBackend), matching the existing Python (PyNeo4jBackend) and TypeScript (TSNeo4jBackend) backends. It answers the JavaAnalysisBackend query surface via Cypher over the graph codeanalyzer-java (>= 2.4.0) emits, populated out of band, with the SDK polling it read-only.

Motivation

Python and TypeScript already have read-only Neo4j backends selected by a typed Neo4jConnectionConfig; Java is the remaining gap. codeanalyzer-java 2.4.0 exposes Neo4j emit, so a Java graph backend can reach parity.

Scope

• cldk/analysis/java/neo4j/: JNeo4jBackend + reconstruct.py (+ shared Neo4jConnectionConfig).
• Wire CLDK.java(..., backend=Neo4jConnectionConfig(...)) / JavaAnalysis backend selection.
• Tests: selection + ABC contract (mirroring Python/TS); skip-by-default integration parity.
• README: mermaid diagram + backends table.

References

• Python backend: cldk/analysis/python/neo4j/
• TypeScript backend: cldk/analysis/typescript/neo4j/