feat: add configurable download path system with templates and mappings

Implements a new download path configuration UI and backend logic:
- Add Subfolder fill mode: Suggested (existing), Template, Manual
- Add Base Model Path Mappings to override detected base-model folders
- Add Default Root settings to control root directory per category
- Add Detect From Existing Folders button that infers templates and mappings from local model folders
- Add backend /model_resolver/root-directories and /model_resolver/path-template-suggestions routes
- Refactor resolver settings into core/settings.py for shared frontend/backend use
- Extract path template inference logic into core/path_templates.py
- Update download panel, context menu, and loading flow to use new path settings

web/resolver/shell/lifecycle_graph_methods.js

@@ -157,6 +157,7 @@ export const lifecycleGraphMethods = {
                 this.cachedAnalysisData
             ) {
                 if (shouldRenderMissingModels()) {
+                    await this.ensureDownloadDirectoriesLoaded();
                     this.displayMissingModels(this.contentElement, this.cachedAnalysisData);
                     this.reconnectActiveDownloads();
                 }
@@ -197,6 +198,7 @@ export const lifecycleGraphMethods = {
                 this.saveAnalysisCacheForActiveWorkflow();
             }
             if (shouldRenderMissingModels()) {
+                await this.ensureDownloadDirectoriesLoaded();
                 this.displayMissingModels(this.contentElement, data);
 
                 // Reconnect any active downloads to their new progress divs