feat(connections): edit existing connection (host, auth, SSL, …)

[ZhuchkaTriplesix]

Problem

Once a connection is saved, the sidebar context menu only offers Refresh (databases / tree) and Remove connection. There is no Edit / Properties path to change host, port, user, password, database, SSL, display name, or URL-derived fields.

Workaround today: delete the connection and create it again — loses tree expand state, recent usage, and is error-prone for password/SSL tweaks.

Current state

• Create flows exist: New Connection dialog, URL dialog, SQLite form (connection_creation_flow.dart, new_connection_*.dart, sqlite_connection_form.dart).
• Storage already supports updates: LocalDb.updateConnection (+ secure-store secret sync, covered by tests).
• UI never calls updateConnection for an existing row — connection tiles only wire onRemove / refresh.

Proposal

1. Add Edit connection… to the connection context menu (all drivers + extension tiles + plain _ConnectionTile).
2. Open a pre-filled edit dialog (reuse create forms where practical; keep type read-only or disallow driver change in v1).
3. On save: LocalDb.updateConnection, refresh sidebar label/metadata, reconnect or invalidate the live pool if the connection is active.
4. Optional later: “Duplicate connection…”, edit-from-URL paste.

Files (starting points)

• lib/features/connections/connections_panel_*.dart (context menus)
• lib/features/connections/connection_creation_flow.dart / form dialogs
• lib/core/storage/local_db.dart (updateConnection — already present)
• lib/core/storage/connection_secrets_store.dart

Acceptance

• Context menu: Edit connection… on saved connections
• Dialog opens with current values (secrets: show empty / “unchanged” pattern — don’t leak stored password into UI unless user replaces it)
• Save persists via updateConnection and updates the sidebar without requiring delete+recreate
• Active connection: safe reconnect or clear stale session after credential/host change
• Cancel leaves connection unchanged
• Works for built-in drivers (PG/MySQL/Redis/Mongo/SQLite) and extension driver connections where a form exists

Out of scope (v1)

• Changing connection type/driver in place
• Bulk edit

[ZhuchkaTriplesix]

Shipped in #517