feat(P02): l1-cloudwatch manifest + mock_apply (T-2.8)

---ci---
phase: 2
milestone: v1.0
status: execute
persona: infra-stub-engineer
task: T-2.8
requirements:
  covered: [REQ-02, REQ-03]
---/ci---

Wave 1, task T-2.8. Creates modules/l1/l1-cloudwatch/ with manifest.yaml
(flat inputs per D-017) and the uniform mock_apply.sh (D-007 + D-018).

modules/l1/l1-cloudwatch/manifest.yaml

@@ -0,0 +1,10 @@
+name: l1-cloudwatch
+kind: l1
+description: Observability primitive
+inputs:
+  log_group_name:
+    description: Name of the CloudWatch log group
+    type: string
+  metric_namespace:
+    description: Namespace under which custom metrics are emitted
+    type: string

modules/l1/l1-cloudwatch/mock_apply.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+echo "[L1: l1-cloudwatch] applying..."
+sleep 1
+echo "[L1: l1-cloudwatch] OK"
+exit 0