feat(settings): filename templates for download and bulk rename (#1071)

Add per-model-type filename templates ({model_name}, {version_name},
{base_model}, {author}, {first_tag}, {hash_short}, {original_name}) so
downloaded files get informative names instead of e.g. V1.safetensors.
Empty template keeps the current filename (opt-in, off by default).

- apply template automatically after downloads; rename conflicts keep
  the original name and never fail the download
- record original_file_name in metadata on rename for traceability
- bulk apply via GET|POST /api/lm/{prefix}/apply-filename-template with
  WebSocket progress, sharing the auto-organize lock
- settings UI lives in the new Organization tab with validation, live
  preview, and per-type 'apply to library' actions

tests/frontend/managers/settingsManager.modelPaths.test.js

@@ -36,6 +36,8 @@ vi.mock('../../../static/js/utils/constants.js', () => ({
     DEFAULT_PATH_TEMPLATES: {},
     MAPPABLE_BASE_MODELS: [],
     PATH_TEMPLATE_PLACEHOLDERS: {},
+    FILENAME_TEMPLATE_PLACEHOLDERS: [],
+    DEFAULT_FILENAME_TEMPLATES: { lora: '', checkpoint: '', embedding: '' },
     DEFAULT_PRIORITY_TAG_CONFIG: {},
     getMappableBaseModelsDynamic: () => [],
 }));