Write the name in lowercase where people see it

The brand is lowercase inbuxa. This changes what the app calls itself by
default, the wordmark's accessible name, the sign-in card's version line, the
installed app's name in the manifest, and the four translated strings that
name the console or the mail server.

Those four are source strings, so their catalog keys changed with them in all
nine languages; the translations keep their text with the name corrected. No
key was left behind, and no language falls back on more strings than before:
1643/1662 translated, 19 falling back, in each of the nine, unchanged.

Code identifiers, capability URNs, env var names and comments are untouched.

web/src/lib/brand.ts

@@ -12,9 +12,9 @@ import { useSession } from "@/store/session";
  * One constant rather than the string written out at each of them, because
  * three copies of a default is how two of them end up stale.
  */
-// ihasmail-inbuxa: INBUXA's webmail goes by INBUXA, so it can't be taken for
+// ihasmail-inbuxa: inbuxa's webmail goes by inbuxa, so it can't be taken for
 // public ihasmail. APP_NAME still names a deployment whatever it likes.
-export const DEFAULT_APP_NAME = "INBUXA";
+export const DEFAULT_APP_NAME = "inbuxa";
 /**
  * What this instance calls itself, right now.
  *