test(saas): Phase 1 integration tests — billing + scheduled_task + knowledge (68 tests)

- Fix TIMESTAMPTZ decode errors: add ::TEXT cast to all SELECT queries
  where Row structs use String for TIMESTAMPTZ columns (~22 locations)
- Fix Axum 0.7 route params: {id} → :id in billing/knowledge/scheduled_task routes
- Fix JSONB bind: scheduled_task INSERT uses ::jsonb cast for input_payload
- Add billing_test.rs (14 tests): plans, subscription, usage, payments, invoices
- Add scheduled_task_test.rs (12 tests): CRUD, validation, isolation
- Add knowledge_test.rs (20 tests): categories, items, versions, search, analytics, permissions
- Fix auth test regression: 6 tests were failing due to TIMESTAMPTZ type mismatch

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -16,7 +16,7 @@ pub async fn ingest_telemetry(
     entries: &[TelemetryEntry],
 ) -> SaasResult<TelemetryReportResponse> {
     // 预验证所有条目，分离有效/无效
-    let now = chrono::Utc::now().to_rfc3339();
+    let now = chrono::Utc::now();
     let mut rejected = 0usize;
     let valid: Vec<&TelemetryEntry> = entries.iter().filter(|e| {
         if e.input_tokens < 0 || e.output_tokens < 0 || e.model_id.is_empty() {
@@ -237,8 +237,7 @@ pub async fn get_daily_stats(
     let from_ts = (chrono::Utc::now() - chrono::Duration::days(days))
         .date_naive()
         .and_hms_opt(0, 0, 0).unwrap()
-        .and_utc()
-        .to_rfc3339();
+            .and_utc();
 
     let sql = "SELECT
         reported_at::date::text as day,