feat: add live connection testing for database and network URLs during interactive setup

[hammadmajid]

Problem

Developers frequently enter connection strings (PostgreSQL, MySQL, Redis, RabbitMQ, HTTP APIs) with typos or wrong ports and only discover the failure when attempting to boot the application.

Proposed Solution

Add an optional connection probing action in the interactive TUI that tests network reachability for supported protocol schemes (e.g. postgres://, mysql://, redis://, http://, https://).

Expected Behavior

• When focusing on a variable with a URL connection string, a keybinding (e.g. Ctrl+T) triggers a non-destructive handshake/ping to the target service.
• The TUI displays a brief status badge: Connected (service version/pong) or Connection failed (error message).

Acceptance Criteria

• Probing operations enforce a strict timeout (e.g. 3-5 seconds) and do not block or freeze the TUI.
• Probing is non-destructive (uses ping / handshake protocols only, no write operations).
• Optional format validation rules (e.g. # @validate url, # @validate email) enforce valid syntax before submission.