feat(tauri): Postgres object detail views (functions, indexes, triggers, …) #1981

Parent

#1848

Goal

Open Flutter-parity detail/browser panes when selecting Postgres tree nodes: function DDL, sequence metadata, schema Indexes/Triggers/Types lists, and single index/trigger/type rows.

Done when

• Clicking Functions → item shows pg_get_functiondef text
• Clicking Indexes / Triggers / Types folders shows schema listings
• Clicking a sequence shows metadata + current value
• Unit/live tests for detail fetch on shop schema

How to work

• Branch from epic/tauri-migration
• PR base: epic/tauri-migration