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/api/routes/edges.py

@@ -0,0 +1,46 @@
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.api.deps import get_current_user
+from app.db.database import get_db
+from app.db.models import Edge
+from app.schemas.edges import EdgeCreate, EdgeResponse, EdgeUpdate
+
+router = APIRouter()
+
+
+@router.get("/", response_model=list[EdgeResponse])
+async def list_edges(db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)):
+    result = await db.execute(select(Edge))
+    return result.scalars().all()
+
+
+@router.post("/", response_model=EdgeResponse, status_code=status.HTTP_201_CREATED)
+async def create_edge(body: EdgeCreate, db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)):
+    edge = Edge(**body.model_dump())
+    db.add(edge)
+    await db.commit()
+    await db.refresh(edge)
+    return edge
+
+
+@router.delete("/{edge_id}", status_code=status.HTTP_204_NO_CONTENT)
+async def delete_edge(edge_id: str, db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)):
+    edge = await db.get(Edge, edge_id)
+    if not edge:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Edge not found")
+    await db.delete(edge)
+    await db.commit()
+
+
+@router.patch("/{edge_id}", response_model=EdgeResponse)
+async def update_edge(edge_id: str, body: EdgeUpdate, db: AsyncSession = Depends(get_db), _: str = Depends(get_current_user)):
+    edge = await db.get(Edge, edge_id)
+    if not edge:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Edge not found")
+    for field, value in body.model_dump(exclude_unset=True).items():
+        setattr(edge, field, value)
+    await db.commit()
+    await db.refresh(edge)
+    return edge