feat(billing): activate real-time quota enforcement pipeline

- Wire relay handler to increment_usage() for JSON responses (tokens + relay_requests)
- Wire relay handler to increment_dimension("relay_requests") for SSE streams
- Add increment_dimension() function for hand_executions/pipeline_runs dimensions
- Schedule AggregateUsageWorker hourly for reconciliation (run_on_start=true)
- Mount mock payment routes in dev mode (ZCLAW_SAAS_DEV=true)

Previously the quota middleware always allowed requests because usage
counters were never incremented. Now relay requests update billing_usage_quotas
in real-time, with the aggregator providing hourly reconciliation.

crates/zclaw-saas/src/billing/service.rs

@@ -146,7 +146,10 @@ pub async fn get_or_create_usage(pool: &PgPool, account_id: &str) -> SaasResult<
     Ok(usage)
 }
 
-/// 增加用量计数
+/// 增加用量计数（Relay 请求：tokens + relay_requests +1）
+///
+/// 在 relay handler 响应成功后直接调用，实现实时配额更新。
+/// 聚合器 `AggregateUsageWorker` 每小时做一次对账修正。
 pub async fn increment_usage(
     pool: &PgPool,
     account_id: &str,
@@ -170,6 +173,39 @@ pub async fn increment_usage(
     Ok(())
 }
 
+/// 增加单一维度用量计数（hand_executions / pipeline_runs / relay_requests）
+///
+/// 使用静态 SQL 分支（白名单），避免动态列名注入风险。
+pub async fn increment_dimension(
+    pool: &PgPool,
+    account_id: &str,
+    dimension: &str,
+) -> SaasResult<()> {
+    let usage = get_or_create_usage(pool, account_id).await?;
+
+    match dimension {
+        "relay_requests" => {
+            sqlx::query(
+                "UPDATE billing_usage_quotas SET relay_requests = relay_requests + 1, updated_at = NOW() WHERE id = $1"
+            ).bind(&usage.id).execute(pool).await?;
+        }
+        "hand_executions" => {
+            sqlx::query(
+                "UPDATE billing_usage_quotas SET hand_executions = hand_executions + 1, updated_at = NOW() WHERE id = $1"
+            ).bind(&usage.id).execute(pool).await?;
+        }
+        "pipeline_runs" => {
+            sqlx::query(
+                "UPDATE billing_usage_quotas SET pipeline_runs = pipeline_runs + 1, updated_at = NOW() WHERE id = $1"
+            ).bind(&usage.id).execute(pool).await?;
+        }
+        _ => return Err(crate::error::SaasError::InvalidInput(
+            format!("Unknown usage dimension: {}", dimension)
+        )),
+    }
+    Ok(())
+}
+
 /// 检查用量配额
 pub async fn check_quota(
     pool: &PgPool,