Implement V2 registration support (#7765)

* Implement V2 registration support

* Require the client version header on every login, like upstream

Every user login (password, user API key, SSO, including a first SSO login)
now needs the Bitwarden-Client-Version header, for V1 accounts too. V2
accounts need 2026.10.1, or 2026.10.2 for the desktop app, upstream's
current minimum.

* Escape the email in the client version log line

On a first SSO login the email comes from the identity provider and isn't validated yet, so a newline in it could add a line to the log.

src/db/models/mod.rs

@@ -17,6 +17,7 @@ mod two_factor;
 mod two_factor_duo_context;
 mod two_factor_incomplete;
 mod user;
+mod user_signature_key_pair;
 
 pub use self::archive::Archive;
 pub use self::attachment::{Attachment, AttachmentId};
@@ -42,3 +43,4 @@ pub use self::two_factor::{TwoFactor, TwoFactorType};
 pub use self::two_factor_duo_context::TwoFactorDuoContext;
 pub use self::two_factor_incomplete::TwoFactorIncomplete;
 pub use self::user::{Invitation, KeyId, SsoUser, User, UserId, UserKdfType, UserStampException};
+pub use self::user_signature_key_pair::{SignatureAlgorithm, UserSignatureKeyPair};