feat(canvas): raise switch port cap to 64, add port numbers and fibre edge type

Issue #20: bump MAX_BOTTOM_HANDLES 48 -> 64 (covers 48+4 SFP switches) and add
a per-node "Show Port Numbers" toggle that labels each bottom connection point.

Issue #21: add `fibre` as a first-class edge/connection type (bright cyan with a
subtle glow) alongside ethernet/wifi/iot/vlan/virtual/cluster - selectable in the
edge modal, themeable, registered in the React Flow edgeTypes registry, and
round-tripped through YAML import/export.

Backport of homelable-hacs PR #23.

ha-relevant: yes

frontend/src/utils/canvasSerializer.ts

@@ -32,6 +32,7 @@ export interface ApiNode extends Record<string, unknown> {
   width?: number | null
   height?: number | null
   bottom_handles?: number
+  show_port_numbers?: boolean
 }
 
 export interface ApiEdge {
@@ -114,6 +115,7 @@ export function serializeNode(n: Node<NodeData>): Record<string, unknown> {
     width: n.measured?.width ?? n.width ?? null,
     height: n.measured?.height ?? n.height ?? null,
     bottom_handles: clampBottomHandles(n.data.bottom_handles ?? 1),
+    show_port_numbers: n.data.show_port_numbers ?? false,
     pos_x: n.position.x,
     pos_y: n.position.y,
   }