feat(db): mesh data model — meshes, members, invites, audit log

- pgSchema "mesh" with 4 tables isolating the peer mesh domain
- Enums: visibility, transport, tier, role
- audit_log is metadata-only (E2E encryption enforced at broker/client)
- Cascade on mesh delete, soft-delete via archivedAt/revokedAt

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tooling/github/setup/action.yml

@@ -0,0 +1,32 @@
+name: CI / Setup
+description: Common setup steps for Github Actions
+
+inputs:
+  node-version:
+    description: "Node.js version"
+    required: true
+    default: "22.x"
+  install-packages:
+    description: "Install packages"
+    required: false
+    default: "true"
+
+runs:
+  using: "composite"
+  steps:
+    - name: ✅ Checkout code
+      uses: actions/checkout@v5
+
+    - name: 🎬 Setup pnpm
+      uses: pnpm/action-setup@v4
+
+    - name: 🔨 Setup Node.js ${{ inputs.node-version }}
+      uses: actions/setup-node@v6
+      with:
+        node-version: ${{ inputs.node-version }}
+        cache: "pnpm"
+
+    - name: 🔌 Install
+      if: ${{ inputs.install-packages == 'true' }}
+      shell: bash
+      run: pnpm install