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/public/manifest.webmanifest

@@ -1,7 +1,7 @@
 {
-  "name": "INBUXA",
-  "short_name": "INBUXA",
-  "description": "INBUXA webmail",
+  "name": "inbuxa",
+  "short_name": "inbuxa",
+  "description": "inbuxa webmail",
   "_comment": "JSON has no comments, so: every URL below is relative on purpose. Manifest members resolve against the manifest's own address, so these follow BASE_PATH with nothing substituted into them at build time. Root-absolute values pinned the installed app, its scope and its shortcuts to the domain root whatever the mount was.",
   "_comment_id": "There is deliberately no `id`. It is the one member NOT resolved against this file's address -- the spec resolves it against the origin of start_url, so `./`, `mail` and `/mail` all mean the same thing at the domain root and none of them can name a subpath mount. Adding one would therefore break the same thing the note above describes. Worse, the default id IS start_url, which is already mount-correct: writing an id now would give every installed copy a new identity and orphan it as a second app rather than updating it. If one is ever wanted it has to be substituted at build time from BASE_PATH, and the changeover costs everybody their install.",
   "start_url": "mail",