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

Cargo.toml

@@ -71,6 +71,8 @@ fastcdc = "4.0.0"
 memmap2 = "0.9.10"
 lettre = { version = "0.11.18", default-features = false, features = ["smtp-transport", "tokio1-rustls-tls", "rustls-native-certs", "builder"] }
 idna = "1.1"
+smol_str = { version = "0.3.2", features = ["serde"] }
+accept-language = "3.1.0"
 
 [features]
 default = []