[ENHANCEMENT] Rename repository from 'nostrclient' to 'nostrproxy'

[BenGWeeks]

Related to #44

Following the rename of the extension display name from "Nostr Client" to "Nostr Proxy" (#44), the repository itself should be renamed for consistency.

Proposed Change

• Current: https://github.com/lnbits/nostrclient
• Proposed: https://github.com/lnbits/nostrproxy

Rationale

The name "nostrclient" is misleading - users expect a Nostr client to be an app for viewing/interacting with notes (like Damus, Amethyst). This extension is actually a relay multiplexer/proxy.

Renaming the repo would:

1. Match the new display name ("Nostr Proxy")
2. Better describe the extension's function
3. Reduce confusion for new users

Notes

• GitHub automatically redirects old URLs to new ones after a rename
• Package references and imports would need to be updated

cc @arcbtc

[BenGWeeks]

Also related: #35