Follow the sibling project's rename to dev-updater

It is no longer "local" -- it serves over WireGuard rather than the LAN --
and it is specifically for developing new apps. Renaming the references
here at the same time keeps one name to search for across both repos.

Also drops the last references to gen-dev-cert.sh, which the in-process
certificate generation replaced: the build script and the Gradle task now
say to start the server once, and test-wg-tunnel.sh reads the
certificates from the XDG directory rather than the repo.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017xn8nHw1tw1R6PtiY1eEtw

server/src/main.rs

@@ -193,7 +193,7 @@ async fn main() -> Result<()> {
         tracing::warn!(
             "a new CA was generated in {} -- any installed app pins the previous one and can no \
              longer reach this server. Rebuild it with app/build-apk.sh, which embeds this CA, \
-             and reinstall through Local Updater.",
+             and reinstall through Dev Updater.",
             certs_dir.display(),
         );
     }