INBUXA's name and site where the webmail still said ihasmail

- The sign-in footer names the build "INBUXA webmail" and links to
  inbuxa.org, next to its AGPL source link.
- About gives the INBUXA webmail version, and credits ihasmail on a line
  of its own.
- The user menu's "About ihasmail" is "About INBUXA", to inbuxa.org. The
  Documentation entry pointed at ihasmail's docs; it's gone until INBUXA
  has documentation of its own.
- The startup log says "mail server:" rather than naming the server
  software.

"About INBUXA" and "Built on {ihasmail}" are translated in all nine
catalogues.

server/src/index.ts

@@ -7,7 +7,7 @@ async function main() {
   const app = createApp();
   const server = serve({ fetch: app.fetch, hostname: config.host, port: config.port }, (info) => {
     console.log(`[ihasmail] ${config.appName} listening on http://${info.address}:${info.port}`);
-    console.log(`[ihasmail] upstream Stalwart: ${config.stalwartUrl}`);
+    console.log(`[ihasmail] mail server: ${config.stalwartUrl}`);
     console.log(`[ihasmail] static dir: ${config.staticDir}`);
   });