webapp: export Blancco reports for the last 1/3/6/12 months

/reports/export?range=1m|3m|6m|12m&format=csv|zip. CSV has one row per
erased drive (system and drive serials, standard, result, times, licence
consumption id). ZIP holds the original XML/PDF reports plus summary.csv.
Reports are selected by the date inside each XML, falling back to mtime
only when it is missing. Exports are audit-logged.

webapp/app.py

@@ -591,6 +591,79 @@ def blancco_reports():
     )
 
 
+REPORT_EXPORT_RANGES = {"1m": 1, "3m": 3, "6m": 6, "12m": 12}
+
+
+def _months_ago(now, months):
+    # Same day-of-month N months back, clamped (Mar 31 - 1m -> Feb 28/29).
+    import calendar
+    y, m = divmod(now.year * 12 + now.month - 1 - months, 12)
+    day = min(now.day, calendar.monthrange(y, m + 1)[1])
+    return now.replace(year=y, month=m + 1, day=day)
+
+
+@app.route("/reports/export")
+def blancco_export_reports():
+    import csv
+    import io
+    import zipfile
+    from datetime import timezone
+
+    rng = request.args.get("range", "1m")
+    fmt = request.args.get("format", "csv")
+    if rng not in REPORT_EXPORT_RANGES or fmt not in ("csv", "zip"):
+        abort(400)
+    now = datetime.now(timezone.utc)
+    since = _months_ago(now, REPORT_EXPORT_RANGES[rng])
+
+    # Select by the date inside each XML report; fall back to mtime only
+    # when a report has no parseable date. PDFs (7.20 writes pdf+xml) ride
+    # along with the XML of the same name.
+    rows, files = [], []
+    folder = config.BLANCCO_REPORTS
+    names = sorted(os.listdir(folder)) if os.path.isdir(folder) else []
+    for f in names:
+        fpath = os.path.join(folder, f)
+        if not (f.lower().endswith(".xml") and os.path.isfile(fpath)):
+            continue
+        try:
+            data = blancco_report.parse(fpath)
+        except Exception:
+            data = {}
+        when = blancco_report.report_datetime(data) or datetime.fromtimestamp(
+            os.stat(fpath).st_mtime, timezone.utc)
+        if when < since:
+            continue
+        rows.extend(blancco_report.export_rows(f, data, when.isoformat()))
+        files.append(f)
+        pdf = os.path.splitext(f)[0] + ".pdf"
+        if pdf in names:
+            files.append(pdf)
+
+    buf = io.StringIO()
+    writer = csv.DictWriter(buf, fieldnames=blancco_report.EXPORT_COLUMNS)
+    writer.writeheader()
+    writer.writerows(rows)
+    stem = f"blancco-reports-{rng}-{now:%Y%m%d}"
+    audit("REPORT_EXPORT", f"{rng} {fmt} {len(files)} files")
+
+    if fmt == "csv":
+        return Response(
+            buf.getvalue(),
+            mimetype="text/csv",
+            headers={"Content-Disposition": f"attachment; filename={stem}.csv"},
+        )
+    # A year of reports can run to hundreds of MB; spill to disk past 64MB.
+    out = tempfile.SpooledTemporaryFile(max_size=64 * 1024 * 1024)
+    with zipfile.ZipFile(out, "w", zipfile.ZIP_DEFLATED) as zf:
+        zf.writestr(f"{stem}/summary.csv", buf.getvalue())
+        for f in files:
+            zf.write(os.path.join(folder, f), f"{stem}/{f}")
+    out.seek(0)
+    return send_file(out, mimetype="application/zip", as_attachment=True,
+                     download_name=f"{stem}.zip")
+
+
 @app.route("/reports/download/<filename>")
 def blancco_download_report(filename):
     filename = secure_filename(filename)