generate_3d: 3D models with fal.ai (image, text, or image steered by text)

- New tool: image-to-3D (project file or an image attached to the chat,
  optional back/left/right views) or text-to-3D; image + prompt refines the
  image with the prompt first (the 3D models take no text with an image).
  Styles textured / geometry / lowpoly, optional PBR, face count. Runs through
  fal.ai's queue API with progress, saves GLB + preview, books the cost
  (published prices, overridable per model). Request bodies for the Hunyuan3D,
  Tripo and Trellis families; defaults [images] model_3d / model_3d_text.
- Chat card: "Open in the 3D view"; media overview: kind "model" (also
  STL/3MF/OBJ written by agents) with previews.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/i18n/en.ts

@@ -355,6 +355,7 @@ export const en = {
   "media.filter.all": "All",
   "media.filter.image": "Images",
   "media.filter.video": "Videos",
+  "media.filter.model": "3D",
   "media.filter.audio": "Audio",
   "media.source.generated": "generated",
   "media.source.tool": "tool output",
@@ -712,6 +713,7 @@ export const en = {
   "plan.implementPrompt": "Implement the plan.",
 
   "tool.input": "Input",
+  "tool.open3d": "Open in the 3D view",
   "tool.output": "Output",
   "tool.todosUpdated": "Tasks updated ({done}/{total} done)",
   "tool.todos": "Tasks",