Add 3D force graph view mode

Integrates 3d-force-graph / Three.js as a new GraphMode view in the
container block. RDF/XML results are converted to nodes and links,
rendered in an interactive 3D canvas constrained to the .main.span7
column. Supports node click (info panel), double-click (load linked
resources via proxy), hover tooltip, and background click to dismiss.

- Add three.js, three-spritetext, 3d-force-graph UMD bundles (v0.159.0 / v1.8.2 / v1.73.3)
- Add 3d-force-graph.xsl: ForceGraph3D init template, RDF→graph data conversion, node/link mode templates
- Add graph3d.xsl: event handlers (click, dblclick, hover, background), UpdateForceGraph3D, HTTP response handler, tooltip/info panel rendering
- Add normalize-rdfxml.xsl, merge-rdfxml.xsl: RDF/XML normalization and merging pipeline
- Add bs2:Graph template, GraphMode canvas div, CSS rules for .graph-3d-canvas
- Wire graph3d.xsl into client.xsl; add $load-graph3d param to layout.xsl
- Remove obsolete graph.xsl

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: namedgraph

src/main/webapp/static/com/atomgraph/linkeddatahub/css/bootstrap.css

@@ -174,6 +174,7 @@ div[typeof="https://w3id.org/atomgraph/linkeddatahub#XHTML"] .form-horizontal .c
 object { display: block; margin: auto; max-height: 400px; overflow: hidden; width: 100%; }
 .chart-canvas { width: 100%; height: 400px; }
 .chart-canvas .google-visualization-table { width: 100%; }
+.graph-3d-canvas { width: 100%; height: 600px; overflow: hidden; background: #141414; position: relative; }
 .table { display: table; }
 .row { display: table-row ; }
 .cell { display: table-cell ; }