Canvas: snap connection endpoints / arrow heads to fixed anchor points on shape perimeter (e.g. 8 division points)

### Summary In Canvas panel, when drawing connections (arrows, connectors) between shapes (e.g. rectangles), there are visible anchor points on the perimeter of shapes. However, the arrow heads (connection endpoints) do not automatically snap to fixed anchor/port points (such as the 8 division points around the perimeter – N / NE / E / SE / S / SW / W / NW). When multiple arrows are connected to the same shape at the same approximate location, the lack of snap causes messy overlaps or misaligned arrowheads. <img width="523" height="179" alt="Image" src="https://github.com/user-attachments/assets/977feb93-f86d-431e-8562-2912ae891cb7" /> ### Expected Behavior - When dragging a connection from one shape to another, the arrowhead endpoint should snap to the nearest predefined anchor point on the perimeter of the target shape. - If multiple connections approach from similar directions, they should evenly distribute or align at those anchor points to improve visual clarity. - Option to enable/disable this “snap-to-anchor” behavior. ### Actual Behavior - Arrowhead endpoints remain wherever the mouse/touch is released, even if very close to a logical anchor point. - Overlaps / slightly misaligned endpoints occur when connecting multiple arrows manually. ### Use Case / Why This Matters - In visual diagrams (flows, architectures) where clarity matters, clean and consistent connection points greatly improve readability. - Users expect behavior similar to diagram tools (e.g. draw.io, etc.) where shapes provide anchor points and connectors snap automatically. ### Environment - Grafana version: v12.0.1 - Canvas panel version / environment: Self-hosted - Browser: Chrome ### Possible Implementation Ideas (optional) - Define anchor points around shape perimeters (e.g. 8-way compass points) for standard shapes (rectangle, ellipse). - When connection endpoint is dragged within certain radius of an anchor, auto-snap there. - Maybe even display anchor highlight when close.