fix(paths): keep business paths forward-slashed on Windows

Four places produced the host's separator (or a mixed path) where the app's
business form is forward-slashed, so on Windows the value could not be compared
with the one the rest of the app stores:

* `ModelScanner._calculate_folder` matched `file_path.startswith(root)` as raw
  strings, so every forward-slashed path resolved to the library root and a
  moved model was filed under the root instead of its folder. It now compares
  root identities and slices the relative part off.
* `normalize_relative_folder` ran `os.path.normpath`, and ntpath folds forward
  slashes back to backslashes: every folder parameter (scoped scan, create,
  rename, delete) came back host-spelled and mismatched the stored folders.
* `_format_model_name_for_comfyui` returned `os.path.relpath` unchanged, so the
  checkpoint/unet nodes and the metadata node emitted `unet\base.safetensors`
  on Windows -- a name no ComfyUI widget list matches.
* `resolve_centralized_dir_for_dir` passed a component that spans two
  directories ("<library>/<component>") whole to `os.path.join`, leaving a mixed
  path ("...\comfyui/loras-1a2b3c4d\sub") that no native path equals.

Also hands the rename re-key callback business paths, like every other absolute
path the move service returns.

py/services/model_file_service.py

@@ -1,7 +1,8 @@
 import asyncio
 import fnmatch
-import os
 import logging
+import os
+import posixpath
 import shutil
 from typing import Any, Dict, List, Optional, Sequence, Set
 from abc import ABC, abstractmethod
@@ -36,12 +37,11 @@ def normalize_relative_folder(folder: str) -> str:
     if normalized.startswith("/") or (len(normalized) > 1 and normalized[1] == ":"):
         raise ValueError("Folder path must be relative to a library root")
 
-    normalized = os.path.normpath(normalized)
-    if (
-        normalized == ".."
-        or normalized.startswith("../")
-        or normalized.startswith(".." + os.sep)
-    ):
+    # posixpath, not os.path: ntpath.normpath would fold the business form back
+    # to backslashes, and every stored folder, cache entry and comparison in the
+    # app is forward-slashed.
+    normalized = posixpath.normpath(normalized)
+    if normalized == ".." or normalized.startswith("../"):
         raise ValueError("Folder path must stay inside the library root")
 
     return normalized
@@ -1062,7 +1062,12 @@ class ModelMoveService:
 
             new_relative = self._calculate_relative_folder(target)
             await self._rename_folder_records(
-                previous_relative, new_relative, absolute_path, target
+                previous_relative,
+                new_relative,
+                # Business paths, like every other absolute path this service
+                # hands out: the scanner re-keys cache entries by prefix.
+                absolute_path.replace(os.sep, "/"),
+                target.replace(os.sep, "/"),
             )
 
             return {