feat: allow leaving of server

[nexxai]

Summary

Allows a user to leave a guild they are currently a member of

Why

There are guilds that people join that they want to leave for one reason or another

How

I implemented a new section under the server's leader-key menu called "Server management". Currently we only support leaving servers, but if this PR is accepted, there will be a fast-follow PR that supports joining new servers.

Testing

• cargo fmt --all --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --all-features
• Manual test in a real terminal (describe below)

OS: macOS Tahoe 26.5
Terminal: Ghostty 1.3.1

Screenshots or recordings

[LEADER] key is pressed:

s is pressed:

l (lowercase "L") is pressed:

Checklist

• One logical change per PR.
• Link a related issue.
• No tokens, passwords, MFA codes, or raw auth bodies in code, tests, or logs.
• Change does not add self-bot automation, mass actions, or scraping.
• Updated README.md, if behavior or workflows changed.

[nexxai]

Fixed merge conflicts. @chojs23 this is ready for review

[chojs23]

Why don't you put it in the server action?

[nexxai]

@chojs23 Originally I was thinking about adding other tools that would live in the "management" sphere, but for now, I've moved it to the server actions.

[chojs23]

One possible future direction is to keep “Server Management” as a separate action group, where we can add broader server-level settings later.