feat: improve network topology — LLDP-authoritative, manual links, orphan handling (v0.11.6 Beta)

- Backend: 7-step pipeline — per-neighbor best-protocol dedup, bidirectional
  LLDP pair merging, LLDP-covered set suppression of noisy CDP/MNDP links,
  shared-segment heuristic limited to genuinely unresolved non-LLDP links
- Backend: manual_topology_links table + POST/DELETE endpoints for user-drawn connections
- Frontend: ManualEdge custom edge type (purple dashed + × delete button)
- Frontend: Connect Mode toggle — blue crosshair handles, onConnect creates DB-persisted link
- Frontend: orphan nodes in dedicated bottom row with orange warning banner
- Frontend: legend updated, canvas height increased

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/services/api.ts

@@ -400,8 +400,15 @@ export const topologyApi = {
       devices: Device[];
       links: import('../types').TopologyLink[];
       externalNodes: import('../types').ExternalTopologyNode[];
+      segConns: { src: string; dst: string; port: string }[];
+      manualLinkIds: { id: number; from_device_id: number; to_device_id: number }[];
     }>('/topology'),
   discover: () => api.post('/topology/discover'),
+  createManualLink: (from_device_id: number, to_device_id: number, label?: string) =>
+    api.post<{ id: number; from_device_id: number; to_device_id: number; label: string | null }>(
+      '/topology/manual-links', { from_device_id, to_device_id, label }
+    ),
+  deleteManualLink: (id: number) => api.delete(`/topology/manual-links/${id}`),
 };
 
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