fix(maintenance): protect one file reached through two mounts

Re-review of #313, round 2:

- R1: a removal on another device than its kept copy, with the same
  size and mtimes within 2 s, is protected when its inode is equal or its
  path within its source is the same ("May be the same file reached
  through another mount or share"), in the preview and again right before
  each unlink. The job holds the kept copy open during the unlink, so on
  Windows deleting the kept copy itself through another path fails.
- R2: a file's spellings are found by containment: every configured,
  monitored, ComfyUI-output or listed folder whose stat identity is a
  folder above the file. Parent spellings of nested sources and case
  variants match; favorites move under every listed root holding the
  file. Lookups stay index searches.
- m1: a failed unlink's row says the links now name the kept copy.
- m2: a volume with no file ids reads "Can't confirm this is a separate
  file on this drive".

database/duplicate_copies.py

@@ -132,8 +132,9 @@ class DuplicateCopyOperations:
 
         ``move``: ``removed`` and ``kept`` (the spellings each file is linked
         by), ``targets`` (``{removed spelling: kept spelling}``, the spelling
-        a moved record takes; else ``kept_path``), ``favorite`` (``(root key,
-        removed key, kept root key, kept key)`` or None), ``removed_locator``,
+        a moved record takes; else ``kept_path``), ``favorites`` (``(root key,
+        removed key, kept root key, kept key)`` per listed root holding the
+        file), ``removed_locator``,
         ``kept_locator``, ``sha256`` and the kept copy's ``kept_size`` and
         ``kept_mtime_ns``. Returns ``{moved, merged, favorites, tags,
         review}``.
@@ -167,8 +168,8 @@ class DuplicateCopyOperations:
                         ),
                     )
                     counts["moved"] += 1
-            if move.get("favorite"):
-                counts["favorites"] = _move_favorite(conn, *move["favorite"])
+            for favorite in move.get("favorites", ()):
+                counts["favorites"] += _move_favorite(conn, *favorite)
             counts["tags"] = self._move_copy_tags(conn, move)
             for (item_id,) in conn.execute(
                 _PENDING_OF_LOCATOR, (move["removed_locator"],)