feat: add Relations tab with force-directed resource dependency graph (#96)

Add a new "Relations" tab after "Images" that visualizes resource
dependencies within a Helm release as an interactive force-directed graph.
Detects relationships via ownerReferences, *Ref fields, volumes, env refs,
service selectors, ingress backends, and RBAC bindings. External resources
appear as dashed oval ghost nodes. Color-coded by resource category.

Closes #96

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/dashboard/handlers/helmHandlers.go

@@ -182,6 +182,16 @@ func (h *HelmHandler) Images(c *gin.Context) {
 	c.IndentedJSON(http.StatusOK, images)
 }
 
+func (h *HelmHandler) Relations(c *gin.Context) {
+	rel := h.getRelease(c)
+	if rel == nil {
+		return
+	}
+
+	graph := objects.ExtractRelations(rel.Orig.Manifest)
+	c.IndentedJSON(http.StatusOK, graph)
+}
+
 func (h *HelmHandler) RepoVersions(c *gin.Context) {
 	qp, err := utils.GetQueryProps(c)
 	if err != nil {