fix: network diagram editor UX — straight edges, snap-to-grid, ISP in Cloud, group resize

- Straight edges: replace SmoothStepEdge with BaseEdge + getStraightPath so
  connections draw direct diagonal lines instead of orthogonal bent paths
- Snap-to-grid: add snapToGrid/snapGrid=[20,20] to NetworkCanvas so nodes
  align consistently when dragged
- ISP in Cloud: remove standalone "Internet" sidebar section, inject ISP into
  the Cloud category loop with search support and correct item count
- Group node resize: add NodeResizer to GroupNode (subnet/VLAN/site/DMZ),
  handles visible when selected; dimensions saved/restored correctly on
  reload (also fixes group node load bug where type was always 'device')
- DiagramNode type: add nodeType and style optional fields

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

CHANGELOG.md

@@ -4,6 +4,20 @@ All notable changes to ResolutionFlow are documented here.
 
 ## [Unreleased]
 
+## [2026-04-04] Network Diagram Editor UX Improvements
+
+### Added
+- Snap-to-grid (20px) on Network Diagram canvas — nodes align consistently when dragged
+- NodeResizer on group nodes (subnet/VLAN/site/DMZ) — select a group and drag its handles to resize
+- Group node dimensions now saved to and restored from the backend on reload
+
+### Fixed
+- Connection edges now render as straight lines instead of orthogonal bent paths
+- ISP device now appears inside the Cloud category in the sidebar instead of a standalone "Internet" section; respects search and item count
+- Group nodes now restore correctly as `type: 'group'` on diagram load (previously loaded as `type: 'device'`, breaking group display after save)
+
+---
+
 ### Added
 - Tree Templates + Import/Export marketplace (#66)
 - Recurring Issue Detection — client-specific pattern alerts (#60)