feat: add connection picker and multi-connection tab UX

[Koziar]

Related PR

beamlynx/pine-lang#39

Summary

Adds a connection picker dropdown in the header, integrates the new Pine GET /api/v1/connections endpoint, and improves multi-connection tab behavior so each tab can keep its own database while sharing a single Pine server session.

Requires: Pine server with the structured GET /api/v1/connections response (companion PR in pine-lang).

Changes

Connection picker (ActiveConnection)

• Clicking the connection caption opens a dropdown menu instead of the database settings modal.
• Menu lists live connections from Pine with label (e.g. localhost:5432 · myapp_dev) and color dots.
• Add new connection… opens the existing settings modal.

Connection list sync (GlobalStore, HttpClient)

• listConnections() — calls GET /api/v1/connections.
• refreshConnections() — updates global.connections, assigns colors for new ids, and prunes stale entries from connectionColors in localStorage when ids are no longer on the server.
• Refreshed on page load, after connect, and after switch (not on every menu open).

Tab and connection assignment rules

Action	Behavior
Add connection (settings)	If active tab has a pine/SQL expression → new tab. Otherwise assign to active tab.
Pick connection (dropdown)	If active tab has a pine/SQL expression → new tab. If empty → reuse active tab and change its connection via selectConnection.
+ new tab	New empty tab inherits the active tab’s connectionId (not Pine’s global default).

UI polish

• Pine version moved to the top-right next to [Development] / user box.
• Active tab underline uses the tab’s connection color instead of --primary-color.

[vercel]

@Koziar is attempting to deploy a commit to the pine-lang Team on Vercel.

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[Koziar]

PR has some noise due to my prettier, which updates the white spaces in files I touched.