[ENHANCEMENT] Improve Test functionality UX: Add collapsible dialog and cleaner output

[BenGWeeks]

Problem

The current Test functionality in the UI has a few UX issues:

1. Always visible: The test section is displayed at all times, taking up screen real estate even when not in use
2. Unclear purpose: It's not immediately clear that you're sending a test message from one nsec (private key) to an npub (public key)
3. Confusing output: The "Received data" section shows undefined and other raw/confusing data that doesn't help users understand what's happening

Proposed Solution

1. Add a "Test" button at the top of the interface that opens a dialog/modal when clicked
2. Improve labeling to make it clear:
   • "Send from nsec" → clearly indicate this is the sender's private key
   • "Send to npub" → clearly indicate this is the recipient's public key
3. Clean up received data display:
   • Don't show undefined values
   • Format the output in a more human-readable way
   • Perhaps show a simple success/failure message with expandable details for advanced users

Benefits

• Cleaner default UI with less clutter
• Better discoverability of the test feature (dedicated button)
• Improved understanding for users new to Nostr concepts
• More professional appearance without raw/undefined data showing

Screenshots