feat: Phase 1 scaffold — frontend canvas + backend skeleton

Frontend:
- Vite + React 18 + TypeScript + Tailwind v4 + Shadcn/ui
- React Flow v12 canvas with all 11 node types and 5 edge types
- Dark theme with project design system (cyan, green, orange, purple accents)
- Collapsible sidebar, toolbar, detail panel
- Zustand store for canvas state
- Demo data with 10 nodes and 10 edges

Backend:
- FastAPI + SQLAlchemy async + SQLite (Python 3.13)
- DB models: Node, Edge, CanvasState, PendingDevice, ScanRun
- REST API routes: auth, nodes, edges, canvas, scan, status (WebSocket)
- JWT auth + bcrypt via config.yml
- Pydantic v2 schemas

Infra:
- GitHub Actions quality + security workflows
- .gitignore, .env.example, verify-tooling.sh, security-check.sh

backend/app/schemas/nodes.py

@@ -0,0 +1,51 @@
+from datetime import datetime
+from typing import Any
+
+from pydantic import BaseModel
+
+
+class NodeBase(BaseModel):
+    type: str
+    label: str
+    hostname: str | None = None
+    ip: str | None = None
+    mac: str | None = None
+    os: str | None = None
+    status: str = "unknown"
+    check_method: str | None = None
+    check_target: str | None = None
+    services: list[Any] = []
+    notes: str | None = None
+    pos_x: float = 0
+    pos_y: float = 0
+    parent_id: str | None = None
+
+
+class NodeCreate(NodeBase):
+    pass
+
+
+class NodeUpdate(BaseModel):
+    type: str | None = None
+    label: str | None = None
+    hostname: str | None = None
+    ip: str | None = None
+    mac: str | None = None
+    os: str | None = None
+    status: str | None = None
+    check_method: str | None = None
+    check_target: str | None = None
+    services: list[Any] | None = None
+    notes: str | None = None
+    pos_x: float | None = None
+    pos_y: float | None = None
+
+
+class NodeResponse(NodeBase):
+    id: str
+    last_seen: datetime | None = None
+    response_time_ms: int | None = None
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}