feat(providers): add Volcengine Ark usage query with AK/SK signing

Query coding-plan / agent-plan usage for Volcengine Ark via the
control-plane OpenAPI (open.volcengineapi.com), which requires
account-level AccessKey signing rather than the inference API key.

- Implement Volcengine Signature V4 (an AWS SigV4 variant: fixed
  canonical header order, "HMAC-SHA256" algorithm without the AWS4
  prefix, scope ending in "request", service "ark") in
  services/coding_plan.rs
- Auto-detect the plan by probing GetAFPUsage (Agent Plan, AFP
  five-hour/weekly/monthly quotas) first, falling back to
  GetCodingPlanUsage (Coding Plan, session/weekly/monthly percentages);
  a single credential covers whichever plan the account holds
- Parse the real response shape: the window label lives in the `Level`
  field; guard ResetTimestamp <= 0 (session returns -1)
- Store account-level credentials on UsageScript (accessKeyId /
  secretAccessKey), threaded through both the test command and the
  TOKEN_PLAN auto-refresh path
- Add an independent AK/SK input block with a detailed hint pointing to
  the Volcengine console -> API Access Keys
- Add the `monthly` tier label (frontend TIER_I18N_KEYS + tray
  TIER_LABEL_GROUPS + subscription service)
- Sync zh / en / ja / zh-TW locales and the usage-query docs

src-tauri/src/commands/coding_plan.rs

@@ -4,6 +4,15 @@ use crate::services::subscription::SubscriptionQuota;
 pub async fn get_coding_plan_quota(
     base_url: String,
     api_key: String,
+    // 火山方舟用控制面 AK/SK 签名查询用量；其他供应商不传，沿用 api_key。
+    access_key_id: Option<String>,
+    secret_access_key: Option<String>,
 ) -> Result<SubscriptionQuota, String> {
-    crate::services::coding_plan::get_coding_plan_quota(&base_url, &api_key).await
+    crate::services::coding_plan::get_coding_plan_quota(
+        &base_url,
+        &api_key,
+        access_key_id.as_deref(),
+        secret_access_key.as_deref(),
+    )
+    .await
 }

src-tauri/src/commands/provider.rs

@@ -514,9 +514,19 @@ async fn query_provider_usage_inner(
         let (base_url, api_key) =
             resolve_coding_plan_credentials(&app_type, provider, usage_script);
 
-        let quota = crate::services::coding_plan::get_coding_plan_quota(&base_url, &api_key)
-            .await
-            .map_err(|e| format!("Failed to query coding plan: {e}"))?;
+        // 火山方舟用账号 AK/SK 签名查询用量（存于 usage_script，与推理 api_key 分离）；
+        // 其他供应商为 None，service 层沿用 api_key。
+        let access_key_id = usage_script.and_then(|s| s.access_key_id.clone());
+        let secret_access_key = usage_script.and_then(|s| s.secret_access_key.clone());
+
+        let quota = crate::services::coding_plan::get_coding_plan_quota(
+            &base_url,
+            &api_key,
+            access_key_id.as_deref(),
+            secret_access_key.as_deref(),
+        )
+        .await
+        .map_err(|e| format!("Failed to query coding plan: {e}"))?;
 
         // 将 SubscriptionQuota 转换为 UsageResult
         if !quota.success {
@@ -1086,6 +1096,8 @@ mod native_query_credentials_tests {
             template_type: Some("token_plan".to_string()),
             auto_query_interval: None,
             coding_plan_provider: coding_plan_provider.map(str::to_string),
+            access_key_id: None,
+            secret_access_key: None,
         }
     }