add langchain vector sample

[plurzs01]

Working sample for the bank credit-card chatbot use case.

Dozer config uses current main (LocalStorage + SQL unified profile + Dummy/ClickHouse sinks). App does Chroma/local vector retrieval + ranking. Offline path runs without a Dozer binary.

Demo: examples/llm-banking/demo.mp4 (or scripts/demo.sh).

/claim #1690
Fixes #1690

[plurzs01]

hey, this one's ready for a look whenever you have a sec. demo path is offline-friendly if that helps review.

[plurzs01]

also opened the same sample on dozer-samples (where snork-alt said these PRs belong): getdozer/dozer-samples#146

[plurzs01]

keeping this open as a mirror of the dozer-samples PR — prefer reviewing getdozer/dozer-samples#146 (snork-alt's preferred repo). happy to close this one if you'd rather consolidate there.

[plurzs01]

gentle bump — the samples-side claim is ready at getdozer/dozer-samples#146 (offline tests + demo). happy to close this mirror if you prefer everything on the samples repo.

[plurzs01]

mirror note only — real claim is getdozer/dozer-samples#146. fine to close this one if you want everything on samples.

[plurzs01]

mirror only — claim lives on getdozer/dozer-samples#146. ok to close this if you'd rather keep review there.