feat: layout hamburger, media browser filters+previews, billing fixes

- Layout: mobile hamburger menu + overlay backdrop + close button; content area always full-width
- Media browser: filter chips (default still+turntable); advanced toggle for GLB/STL; thumbnail_url previews for non-image types; video hover-play for turntable
- Backend: asset_types multi-filter, thumbnail_url in MediaAssetOut, download proxy endpoint for MinIO/local files
- Admin: "Import Existing Media" button → POST /api/admin/import-media-assets
- Billing: fix invoice create 500 (MissingGreenlet — use selectinload after commit); PDF download uses axios blob instead of bare <a href> (auth header missing); fix storage.upload() accepting str|Path
- SSE task logs: task_logs.py core + router, LiveRenderLog component
- CadPreview: fix infinite loop when no gltf_geometry assets; loading screen before ThreeDViewer render
- render-worker: add trimesh layer to Dockerfile

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

backend/app/domains/billing/router.py

@@ -2,7 +2,7 @@
 from __future__ import annotations
 import uuid
 from fastapi import APIRouter, Depends, HTTPException, status
-from fastapi.responses import RedirectResponse
+from fastapi.responses import Response
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.database import get_db
@@ -83,8 +83,12 @@ async def download_invoice_pdf(
     if not key:
         raise HTTPException(status_code=503, detail="PDF generation unavailable (WeasyPrint not installed)")
     from app.core.storage import get_storage
-    url = get_storage().get_url(key)
-    return RedirectResponse(url=url)
+    pdf_bytes = get_storage().download_bytes(key)
+    return Response(
+        content=pdf_bytes,
+        media_type="application/pdf",
+        headers={"Content-Disposition": f"attachment; filename=invoice-{invoice_id}.pdf"},
+    )
 
 
 @invoice_router.delete("/invoices/{invoice_id}", status_code=status.HTTP_204_NO_CONTENT)

backend/app/domains/billing/schemas.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import uuid
 from datetime import date, datetime
 from decimal import Decimal
-from pydantic import BaseModel
+from pydantic import BaseModel, computed_field
 
 
 class InvoiceLineCreate(BaseModel):
@@ -54,4 +54,11 @@ class InvoiceOut(BaseModel):
     created_at: datetime
     lines: list[InvoiceLineOut] = []
 
+    @computed_field  # type: ignore[misc]
+    @property
+    def pdf_url(self) -> str | None:
+        if self.pdf_key:
+            return f"/api/billing/invoices/{self.id}/pdf"
+        return None
+
     model_config = {"from_attributes": True}

backend/app/domains/billing/service.py

@@ -267,8 +267,7 @@ async def create_invoice(
     invoice.total_net = total_net
     invoice.total_vat = (total_net * vat_rate).quantize(Decimal("0.01"))
     await db.commit()
-    await db.refresh(invoice)
-    return invoice
+    return await get_invoice(db, invoice.id)
 
 
 async def get_invoices(