Add edge selection highlighting and zoom to connected nodes

[Mbeaulne]

Description

Enhanced edge selection and highlighting in the flow canvas to improve visual feedback when working with connections. This PR adds:

1. Visual highlighting of nodes connected to selected edges
2. Automatic zooming to fit selected edge connections
3. Handle-based edge selection (clicking an input/output handle selects all connected edges)
4. Improved edge styling with muted appearance for non-selected edges when any edge is selected
5. Updated edge colors for better visibility and contrast
6. Edge rendering order optimization to ensure selected edges appear on top

Type of Change

• New feature
• Improvement

Checklist

• I have tested this does not break current pipelines / runs functionality
• I have tested the changes on staging

Test Instructions

1. Create a flow with multiple connected nodes
2. Click on an edge to select it and observe:
   • Connected nodes highlight with a purple border and ring
   • View automatically zooms to show the connection
   • Other edges appear muted
3. Click on an input or output handle to select all edges connected to that handle
4. Verify that selected edges appear on top of other edges

[Mbeaulne]

• Add edge selection highlighting and zoom to connected nodes #1609 👈 (View in Graphite)
• master

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