feat(i18n): add i18n on server side

- remove the hardcoded list of locales in favor of a discovry on start time
    - server will stop on badly formatted locale .json
    - add server.* entries for serer side translation

    server side translation will be used for templating and email
    note: no json in some embded html (like in /magic), amount of work was similar

src/common/mod.rs

@@ -1,5 +1,6 @@
 pub mod config;
 pub mod di;
 pub mod errors;
+pub mod locale;
 pub mod mime_detect;
 pub mod stubs;