Auto-analyse STL on job detail load; warn if file missing

- If file exists but has no cache entry, run analyse() on page load
- If file doesn't exist on disk, show a red alert in the File & Geometry card
- Hide Download/Compute buttons when file is missing

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

app/routers/ui.py

@@ -265,13 +265,25 @@ def job_detail(job_id: int, request: Request, db: Session = Depends(get_db)):
     job = db.query(PrintJob).filter(PrintJob.id == job_id).first()
     if not job:
         raise HTTPException(status_code=404, detail="Job not found")
-    stl = db.query(StlCache).filter_by(filename=job.file_name).first() if job.file_name else None
+
+    file_missing = False
+    stl = None
+    if job.file_name:
+        file_path = get_stl_dir() / job.file_name
+        if not file_path.exists():
+            file_missing = True
+        else:
+            stl = db.query(StlCache).filter_by(filename=job.file_name).first()
+            if stl is None and not job.file_name.endswith(".gcode"):
+                stl = analyse(job.file_name, db)
+
     estimation = estimate(stl.volume_ccm, job.job_material) if stl and stl.volume_ccm else None
     return templates.TemplateResponse("job_detail.html", {
         "request": request,
         "active": "jobs",
         "job": job,
         "stl": stl,
+        "file_missing": file_missing,
         "estimation": estimation,
         "printers": db.query(Printer).order_by(Printer.name).all(),
         "brackets": db.query(JobBracket).order_by(JobBracket.name).all(),