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/scheduled_task/service.rs

@@ -58,12 +58,12 @@ pub async fn create_task(
     req: &CreateScheduledTaskRequest,
 ) -> SaasResult<ScheduledTaskResponse> {
     let id = uuid::Uuid::new_v4().to_string();
-    let now = chrono::Utc::now().to_rfc3339();
-    let input_json = req.input.as_ref().map(|v| v.to_string());
+    let now = chrono::Utc::now();
+    let input_json: Option<String> = req.input.as_ref().map(|v| v.to_string());
 
     sqlx::query(
         "INSERT INTO scheduled_tasks (id, account_id, name, description, schedule, schedule_type, target_type, target_id, enabled, input_payload, created_at, updated_at)
-         VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $11)"
+         VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10::jsonb, $11, $11)"
     )
     .bind(&id)
     .bind(account_id)
@@ -93,7 +93,7 @@ pub async fn create_task(
         last_result: None,
         last_error: None,
         last_duration_ms: None,
-        created_at: now,
+        created_at: now.to_rfc3339(),
     })
 }
 
@@ -105,7 +105,7 @@ pub async fn list_tasks(
     let rows: Vec<ScheduledTaskRow> = sqlx::query_as(
         "SELECT id, account_id, name, description, schedule, schedule_type,
                 target_type, target_id, enabled, last_run_at, next_run_at,
-                run_count, last_result, last_error, last_duration_ms, input_payload, created_at
+                run_count, last_result, last_error, last_duration_ms, input_payload, created_at::TEXT
          FROM scheduled_tasks WHERE account_id = $1 ORDER BY created_at DESC"
     )
     .bind(account_id)
@@ -124,7 +124,7 @@ pub async fn get_task(
     let row: Option<ScheduledTaskRow> = sqlx::query_as(
         "SELECT id, account_id, name, description, schedule, schedule_type,
                 target_type, target_id, enabled, last_run_at, next_run_at,
-                run_count, last_result, last_error, last_duration_ms, input_payload, created_at
+                run_count, last_result, last_error, last_duration_ms, input_payload, created_at::TEXT
          FROM scheduled_tasks WHERE id = $1 AND account_id = $2"
     )
     .bind(task_id)
@@ -151,7 +151,7 @@ pub async fn update_task(
     let schedule_type = req.schedule_type.as_deref().unwrap_or(&existing.schedule_type);
     let enabled = req.enabled.unwrap_or(existing.enabled);
     let description = req.description.as_deref().or(existing.description.as_deref());
-    let now = chrono::Utc::now().to_rfc3339();
+    let now = chrono::Utc::now();
 
     let (target_type, target_id) = if let Some(ref target) = req.target {
         (target.target_type.as_str(), target.id.as_str())