Add delete button for draft files in case drafts panel

- Add DELETE /api/cases/{case_number}/exports/{filename} endpoint
- Add useDeleteDraft hook in exports API
- Add trash icon + confirmation dialog in drafts panel UI
- Final files (סופי-) cannot be deleted as a safety measure

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/app.py

@@ -1907,6 +1907,17 @@ async def api_download_export(case_number: str, filename: str):
     )
 
 
+@app.delete("/api/cases/{case_number}/exports/{filename}")
+async def api_delete_export(case_number: str, filename: str):
+    """Delete an exported draft file."""
+    export_dir = config.find_case_dir(case_number) / "exports"
+    path = export_dir / filename
+    if not path.exists() or not path.parent.samefile(export_dir):
+        raise HTTPException(404, "קובץ לא נמצא")
+    path.unlink()
+    return {"deleted": True, "filename": filename}
+
+
 @app.post("/api/cases/{case_number}/exports/upload")
 async def api_upload_export(case_number: str, file: UploadFile = File(...)):
     """Upload a revised version of a draft."""