[feat](trx-rs): show server/client build info in HTTP footer

Add compile-time build dates for trx-server and trx-frontend-http, propagate server build metadata through rig state/snapshot, and render both versions + build dates in the HTTP footer.

Co-authored-by: OpenAI Codex <codex@openai.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/trx-client/trx-frontend/trx-frontend-rigctl/src/server.rs

@@ -657,6 +657,7 @@ mod tests {
             initialized: true,
             server_callsign: None,
             server_version: None,
+            server_build_date: None,
             server_latitude: None,
             server_longitude: None,
             pskreporter_status: None,