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

static/js/utils/constants.js

@@ -360,6 +360,25 @@ export const DEFAULT_PATH_TEMPLATES = {
     other: ''
 };
 
+// Valid placeholders for download filename templates (opt-in rename of
+// downloaded safetensors; the result is a filename stem, no path separators)
+export const FILENAME_TEMPLATE_PLACEHOLDERS = [
+    '{model_name}',
+    '{version_name}',
+    '{base_model}',
+    '{author}',
+    '{first_tag}',
+    '{hash_short}',
+    '{original_name}'
+];
+
+// Default filename templates per model type; empty string keeps the original filename
+export const DEFAULT_FILENAME_TEMPLATES = {
+    lora: '',
+    checkpoint: '',
+    embedding: ''
+};
+
 // Model type labels for UI
 export const MODEL_TYPE_LABELS = {
     lora: 'LoRA Models',