fix: resolve clippy warnings for dead field and struct prefix

- Remove unused passkey_name from RegisterStartRequest (only used in RegisterFinishRequest)
- Rename AiUsageView fields from total_calls/total_tokens/total_cost to calls/tokens/cost

src/application/routes/api/webauthn.rs

@@ -25,7 +25,6 @@ const SESSION_COOKIE_NAME: &str = "brewlog_session";
 pub struct RegisterStartRequest {
     pub token: String,
     pub display_name: String,
-    pub passkey_name: String,
 }
 
 #[derive(Serialize)]

src/application/routes/app/account.rs

@@ -14,9 +14,9 @@ use crate::application::server::AppState;
 
 #[derive(Serialize)]
 pub struct AiUsageView {
-    pub total_calls: i64,
-    pub total_tokens: String,
-    pub total_cost: String,
+    pub calls: i64,
+    pub tokens: String,
+    pub cost: String,
 }
 
 fn format_cost(cost: f64) -> String {
@@ -133,9 +133,9 @@ pub(crate) async fn account_page(
         }
     };
     let ai_usage = ai_usage.filter(|s| s.total_calls > 0).map(|s| AiUsageView {
-        total_calls: s.total_calls,
-        total_tokens: format_number(s.total_tokens),
-        total_cost: format_cost(s.total_cost),
+        calls: s.total_calls,
+        tokens: format_number(s.total_tokens),
+        cost: format_cost(s.total_cost),
     });
 
     let template = AccountTemplate {

templates/pages/account.html

@@ -224,15 +224,15 @@
   <div class="grid grid-cols-1 md:grid-cols-3 gap-3">
     <div class="rounded-lg border bg-surface p-4">
       <span class="block text-sm text-stone-500">Total Cost</span>
-      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.total_cost }}</span>
+      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.cost }}</span>
     </div>
     <div class="rounded-lg border bg-surface p-4">
       <span class="block text-sm text-stone-500">API Calls</span>
-      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.total_calls }}</span>
+      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.calls }}</span>
     </div>
     <div class="rounded-lg border bg-surface p-4">
       <span class="block text-sm text-stone-500">Total Tokens</span>
-      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.total_tokens }}</span>
+      <span class="mt-1 block text-lg font-semibold text-stone-800">{{ usage.tokens }}</span>
     </div>
   </div>
 </section>