feat(bulk): reorganize context menu with sections and submenu for workflow actions

Group 15 flat menu items into 5 logical sections (Workflow, Metadata,
Attributes, Organize, Download) with section headers to reduce cognitive
load. Nest the three workflow-related actions (Append, Replace, Copy
Syntax) into a single "Send to Workflow" hover-triggered submenu.

Add submenu infrastructure to BaseContextMenu with mouseover/mouseout
boundary detection, 250ms close delay, and viewport-aware positioning.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

locales/de.json

@@ -696,6 +696,14 @@
             "clear": "Auswahl löschen",
             "skipMetadataRefreshCount": "Überspringen（{count} Modelle）",
             "resumeMetadataRefreshCount": "Fortsetzen（{count} Modelle）",
+            "sendToWorkflow": "An Workflow senden",
+            "sections": {
+                "workflow": "Workflow",
+                "metadata": "Metadaten",
+                "attributes": "Attribute",
+                "organize": "Organisieren",
+                "download": "Download"
+            },
             "autoOrganizeProgress": {
                 "initializing": "Automatische Organisation wird initialisiert...",
                 "starting": "Automatische Organisation für {type} wird gestartet...",