Add SOCKS5 proxy support via [proxy] config

[KaraZajac]

Summary

Adds optional proxy support for Matrix HTTP traffic using reqwest’s socks feature and a new [proxy] section in the config. Users can set a global proxy or override it per profile. If no proxy is configured, behavior is unchanged (no proxy and no use of ALL_PROXY).

Changes

Cargo

• Cargo.toml: Depend on reqwest with the socks feature so the client can use SOCKS5 (and other proxy URLs reqwest supports).

Configuration

• src/config.rs:
  • New ProxyConfig with optional url and a merge() for profile override.
  • IambConfig and ProfileConfig each have an optional proxy: Option<ProxyConfig>.
  • ApplicationSettings gains proxy_url: Option<String>; in load(), global and profile proxy are merged (profile overrides global) and the result is stored in proxy_url.

HTTP client

• src/worker.rs: In create_client_inner, when settings.proxy_url is set, the reqwest client is built with reqwest::Proxy::all(proxy_url). Invalid proxy URL is reported with a clear .expect(...) message at startup.

Docs and examples

• config.example.toml: Added a commented [proxy] example with url = "socks5://127.0.0.1:1080".
• docs/iamb.5: New PROXY section documenting [proxy] and url, and proxy listed as overridable per profile.

Tests

• src/tests.rs: mock_settings() updated so ProfileConfig includes proxy: None and ApplicationSettings includes proxy_url: None.

Usage

• Global: add [proxy] with url = "socks5://host:port" (or another supported proxy URL).
• Per-profile: set proxy = { url = "socks5://..." } under a profile; it overrides the global proxy for that profile.
• Omit [proxy] or leave url unset to use no proxy.

[VAWVAW]

would fix #80 if this wasn't AI slop that ignores the coding style of this project and doesn't even compile (without openssl available).

[KaraZajac]

Hey thanks! I updated the styling and removed the OpenSSL dependency! I hope it looks better. You are correct that I did have AI's help in creating this. Thank you for taking the time to review the code.