This commit introduces the Nostr Development Kit (NDK) to enhance the Nostr client functionality. Key changes include:
- Added `NDKPrivateKeySigner` for improved authentication methods in `LoginModal.svelte` and `App.svelte`.
- Refactored the Nostr client to utilize NDK for connection and event fetching, streamlining the connection process and event handling.
- Updated `go.mod` and `package.json` to include `@nostr-dev-kit/ndk` as a dependency.
- Created a new `package-lock.json` to reflect the updated dependency tree.
These changes improve the overall architecture and maintainability of the Nostr client.
