Feature/itk postgres search tuning

[Elson9]

Summary

APS-4734: add Postgres search ranking and snippet tuning to app-config.production.yaml.

DevHub already uses PostgreSQL and @backstage/plugin-search-backend-module-pg. This change only sets query-time options under the existing search: key:

• highlightOptions — match-centred snippets, up to 2 fragments, shorter length (maxWords: 22, minWords: 10)
• normalization: 1 — stop long documents from dominating ranking
• fragmentDelimiter uses non-breaking spaces so PostgreSQL does not trim the spacing around ...

No plugin, schema, collator, or re-index changes. Auth, catalog, and existing collator config are untouched.

APS tasks included

• APS-4734: Postgres search ranking and snippet tuning

Internal APS PR (merged into this feature branch): bcgov#1

Test evidence

• Same search.pg values validated on the APS PoC (Gold dev) against cloud, security, parks, and API
• After the first pass, snippet length was halved (maxWords 45 → 22, minWords 20 → 10) because results were too verbose
• Before/after for the cloud query. LiDAR (a long dataset record) dropped from 1st to 3rd; Public cloud development guide moved from 3rd to 1st.

Before

After

Impacts

• Config: new search.pg keys in app-config.production.yaml only. Local SQLite (app-config.yaml) ignores them.
• Deployment: no Helm, schema, or re-index change. Query-time only; takes effect on the next image that includes this file.
• Security / privacy: none. No new data stored or exposed.
• Accessibility: uses the existing Backstage search highlight UI; no new colour or interaction pattern.
• Operations: none beyond rolling the image. Collators and Postgres connection are unchanged.