test(e2e): webdav + nextcloud full e2e test coverage

add a full coverage of Webdav and Nextcloud
    purpose: prepare move to Drives and ensure no regression at all

    test scenarios are in docs/plan/BASELINE_TESTS_NC_WEBDAV.md

    current existing bugs identified via these tests:

      ┌──────────┬─────────┬────────────────────────────────────────────────────────────────────────────────────────────────────┐
      │   Bug    │ Surface │                                            Pin location                                            │
      ├──────────┼─────────┼────────────────────────────────────────────────────────────────────────────────────────────────────┤
      │ G4/G5/K5 │ NC      │ AlreadyExists → 500 instead of 412 (handle_move + trashbin restore)                                │
      ├──────────┼─────────┼────────────────────────────────────────────────────────────────────────────────────────────────────┤
      │ G9       │ NC      │ Folder DELETE not row-recursive — orphan descendants stay live                                     │
      ├──────────┼─────────┼────────────────────────────────────────────────────────────────────────────────────────────────────┤
      │ M5/M7    │ Native  │ resolve_path_for_user mismatch — PUT writes, GET reads via lenient lookup, MOVE/DELETE can't find  │
      │          │         │ via strict                                                                                         │
      ├──────────┼─────────┼────────────────────────────────────────────────────────────────────────────────────────────────────┤
      │ M8       │ Native  │ COPY discards destination filename — collides with source                                          │
      ├──────────┼─────────┼────────────────────────────────────────────────────────────────────────────────────────────────────┤
      │ N2       │ Native  │ LOCK creates the token, mutators don't check it — class-2 advertisement is aspirational            │
      └──────────┴─────────┴────────────────────────────────────────────────────────────────────────────────────────────────────┘

tests/common/wipe-storage.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+# Shared helper: wipe a test-storage directory.
+#
+# Source this file (don't execute it):
+#
+#   source "$COMMON/wipe-storage.sh"
+#   wipe_storage "$OXICLOUD_STORAGE_PATH"
+#
+# The path must end in `tests/<name>/storage` (lowercase alphanumeric
+# `<name>`). Anything else is rejected — defends against a typo'd or
+# unexpanded env var feeding the wrong path to `rm -rf`. Examples that
+# pass:
+#
+#   /home/dev/oxicloud/tests/api/storage
+#   /home/dev/oxicloud/tests/webdav/storage
+#   /home/dev/oxicloud/tests/e2e/storage
+#
+# Examples that the sanity check rejects (each would refuse the wipe):
+#
+#   /              — no tests/<x>/storage suffix
+#   $HOME          — same
+#   tests/api      — missing /storage
+#   /tests/storage — missing the <name> segment
+#
+# Postgres state is wiped by `spawn-db.sh` (`docker compose down -v`);
+# this helper is the filesystem equivalent.
+
+wipe_storage() {
+  local path="$1"
+
+  if [[ -z "$path" ]]; then
+    echo "[wipe_storage] ERROR: missing path arg" >&2
+    return 1
+  fi
+
+  # Sanity check: must end in tests/<name>/storage where <name> is
+  # lowercase alphanumeric. Stops `rm -rf` from ever running against
+  # an unexpected expansion of a callerʼs path.
+  if [[ ! "$path" =~ /tests/[a-z0-9]+/storage$ ]]; then
+    echo "[wipe_storage] ERROR: '$path' does not match .../tests/<name>/storage — refusing to wipe" >&2
+    return 1
+  fi
+
+  echo "[wipe_storage] Wipe $path to ensure clean startup"
+  rm -rf "$path"
+  mkdir -p "$path"
+}