feat: add template library for browsing and adding defaults

Replace auto-seed with a browsable template library. Users can
selectively add built-in templates to their collection via a
BookOpen icon or the empty-state prompt. Each library template
tracks its origin via libraryId to prevent duplicates.

- Extract default templates to shared $lib/data/defaultTemplates.ts
- Add GET/POST /api/fitness/templates/library endpoint
- Add library modal with add/added state per template
- Keep seed endpoint as fallback (imports from shared data)

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.24.1",
+	"version": "1.25.0",
 	"private": true,
 	"type": "module",
 	"scripts": {