feat(backend): enhance PostgreSQL CLI protocol support display (#9)

* feat: add protocol support info display to PostgreSQL CLI

- Add comprehensive protocol family groups for PostgreSQL backend
- Display detailed support information with --info flag
- Include PostgreSQL-specific protocols (Extension, Materialized View, pgvector, PostGIS, etc.)

* feat: enhance PostgreSQL CLI protocol support display

- Add support for 'is_*_available' method pattern detection
- Support parameterized methods (explain formats)
- Add PostgreSQL-specific protocol group markers
- Unify JSON output structure with 'database' and 'features' keys
- Mark dialect-specific groups in rich display

* chore: add changelog fragment for PR #9

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: vistart

changelog.d/9.added.md

@@ -0,0 +1 @@
+Add PostgreSQL CLI protocol support display with comprehensive feature information