fix(desktop): raise trait recursion limit for HTTP/2

[bobleer]

Summary

• raise the desktop library crate recursion limit to accommodate the reqwest HTTP/2 and MCP transport type graph
• preserve the recently enabled HTTP/2 streaming support
• document why the non-default compiler budget is required

Root cause

Enabling reqwest HTTP/2 deepened the Send/Sync trait graph reachable from desktop spawned tasks. rustc exhausted the default recursion limit while evaluating the MCP-backed scheduler future and reported E0275.

Verification

• cargo check -p bitfun-desktop
• cargo test -p bitfun-desktop (205 passed, 2 ignored)