feat: add interactive ProcessDiagram SVG component (sub-project 1/3)

New interactive route diagram component with SVG rendering using
server-computed ELK layout coordinates. TIBCO BW5-inspired top-bar
card node style with zoom/pan, hover toolbars, config badges, and
error handler sections below the main flow.

Backend: add direction query parameter (LR/TB) to diagram render
endpoints, defaulting to left-to-right layout.

Frontend: 14-file ProcessDiagram component in ui/src/components/
with DiagramNode, CompoundNode, DiagramEdge, ConfigBadge, NodeToolbar,
ErrorSection, ZoomControls, and supporting hooks. Dev test page at
/dev/diagram for validation.

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/diagram/ElkDiagramRenderer.java

@@ -112,7 +112,7 @@ public class ElkDiagramRenderer implements DiagramRenderer {
 
     @Override
     public String renderSvg(RouteGraph graph) {
-        LayoutResult result = computeLayout(graph);
+        LayoutResult result = computeLayout(graph, Direction.DOWN);
         DiagramLayout layout = result.layout;
 
         int svgWidth = (int) Math.ceil(layout.width()) + 2 * PADDING;
@@ -153,21 +153,27 @@ public class ElkDiagramRenderer implements DiagramRenderer {
 
     @Override
     public DiagramLayout layoutJson(RouteGraph graph) {
-        return computeLayout(graph).layout;
+        return computeLayout(graph, Direction.RIGHT).layout;
+    }
+
+    @Override
+    public DiagramLayout layoutJson(RouteGraph graph, String direction) {
+        Direction dir = "TB".equalsIgnoreCase(direction) ? Direction.DOWN : Direction.RIGHT;
+        return computeLayout(graph, dir).layout;
     }
 
     // ----------------------------------------------------------------
     // Layout computation
     // ----------------------------------------------------------------
 
-    private LayoutResult computeLayout(RouteGraph graph) {
+    private LayoutResult computeLayout(RouteGraph graph, Direction rootDirection) {
         ElkGraphFactory factory = ElkGraphFactory.eINSTANCE;
 
         // Create root node
         ElkNode rootNode = factory.createElkNode();
         rootNode.setIdentifier("root");
         rootNode.setProperty(CoreOptions.ALGORITHM, "org.eclipse.elk.layered");
-        rootNode.setProperty(CoreOptions.DIRECTION, Direction.DOWN);
+        rootNode.setProperty(CoreOptions.DIRECTION, rootDirection);
         rootNode.setProperty(CoreOptions.SPACING_NODE_NODE, NODE_SPACING);
         rootNode.setProperty(CoreOptions.SPACING_EDGE_NODE, EDGE_SPACING);
         rootNode.setProperty(CoreOptions.HIERARCHY_HANDLING, HierarchyHandling.INCLUDE_CHILDREN);