Analyse STL/3MF on upload: bounding box + volume, cached in stl_cache

- StlCache model: filename, cube_x/y/z (mm), volume_ccm
- Migration 0007: stl_cache table
- app/stl_analysis.py: trimesh-based analyse() + get_cache_map()
  - Runs immediately after upload in both /jobs and /brackets/{id}/jobs
  - Skips .gcode (no geometry), caches per filename, idempotent
- Library selector in both modals now shows dimensions and volume
- requirements: trimesh==4.5.3

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

app/stl_analysis.py

@@ -0,0 +1,47 @@
+import logging
+from pathlib import Path
+
+from sqlalchemy.orm import Session
+
+from app.models.stl_cache import StlCache
+
+logger = logging.getLogger("pops")
+
+_ANALYSABLE = {".stl", ".3mf"}
+
+
+def analyse(filename: str, db: Session) -> StlCache | None:
+    """Return cached analysis for filename, computing it if missing."""
+    existing = db.query(StlCache).filter(StlCache.filename == filename).first()
+    if existing:
+        return existing
+
+    from app.stl import get_stl_dir
+    filepath = get_stl_dir() / filename
+    if Path(filename).suffix.lower() not in _ANALYSABLE or not filepath.exists():
+        return None
+
+    try:
+        import trimesh
+        mesh = trimesh.load(str(filepath), force="mesh")
+        extents = mesh.extents          # [size_x, size_y, size_z] in mm
+        volume_mm3 = abs(mesh.volume)   # mm³ (negative for inverted normals)
+        entry = StlCache(
+            filename=filename,
+            cube_x=round(float(extents[0]), 2),
+            cube_y=round(float(extents[1]), 2),
+            cube_z=round(float(extents[2]), 2),
+            volume_ccm=round(volume_mm3 / 1000, 3),
+        )
+        db.add(entry)
+        db.commit()
+        return entry
+    except Exception:
+        logger.exception("STL analysis failed for %s", filename)
+        return None
+
+
+def get_cache_map(filenames: list[str], db: Session) -> dict[str, StlCache]:
+    """Bulk-fetch cached entries for a list of filenames."""
+    rows = db.query(StlCache).filter(StlCache.filename.in_(filenames)).all()
+    return {r.filename: r for r in rows}