login: guessing from elsewhere no longer slows a browser already in use

The login throttle was one counter for everyone, so a stranger failing
on purpose every thirty seconds kept the owner on 429s too. A browser
that logs in now gets a signed diary_device cookie (__Host- over HTTPS,
SameSite=Strict, 400 days), and a login carrying a valid one is slowed
only by its own throttle. Everything else shares the anonymous one, as
before. At most 64 known browsers are tracked; the least recently used
is forgotten first. The failed-login mail says which kind of browser
the failures came from.

src/state.rs

@@ -3,7 +3,11 @@ use std::sync::{atomic::AtomicI64, Arc};
 use sqlx::SqlitePool;
 
 use crate::{
-    auth::Sessions, backup::Backup, config::Config, notify::Notifier, throttle::LoginThrottle,
+    auth::Sessions,
+    backup::Backup,
+    config::Config,
+    notify::Notifier,
+    throttle::{LoginThrottle, LoginThrottles},
     vault::Vault,
 };
 
@@ -11,7 +15,7 @@ use crate::{
 pub struct AppState {
     pub db: SqlitePool,
     pub config: Arc<Config>,
-    pub login_throttle: Arc<LoginThrottle>,
+    pub login_throttle: Arc<LoginThrottles>,
     /// The vault password gets the same slowing-down as the login, kept apart
     /// so guessing at one does not slow the other.
     pub vault_throttle: Arc<LoginThrottle>,