A field build is now self-identifying. `run_gui` logs `PeerSpeak v<version>
starting` (from env!("CARGO_PKG_VERSION")) on launch, and the Settings panel
shows a muted `PeerSpeak v<version>` footer — pinned to the bottom of the
220px category sidebar (wide layout) and appended under the body in the narrow
(<820px) layout. Compile-time string, no new test, no deps, local-only.
Renders the current crate version, so it tracks the Cargo.toml bump at each
release cut (shows v0.6.1 until 0.6.2 is stamped in Track A).
Codex-implemented (gpt-5.5 xhigh), senior-reviewed.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>