feat: refactor skills API and database schema

- Replaced file-based skill category loading with API calls in the GET and POST methods of the skills route.
- Added new `SkillsService` for handling skill category operations.
- Updated SQL initialization script to create `skill_categories`, `skills`, and `skill_links` tables with appropriate relationships.
- Enhanced `ApiClient` with methods for loading skill categories and creating new skills, improving API interaction.
- Introduced error handling for skill category creation and loading processes.

lib/data-loader.ts

@@ -13,6 +13,15 @@ export async function loadSkillCategories(): Promise<SkillCategory[]> {
   }
 }
 
+/**
+ * Load skill categories from local files (fallback or development mode)
+ * This is a client-side safe alternative that still uses the API
+ * For server-side file loading, use loadSkillCategoriesFromFiles from skill-file-loader
+ */
+export async function loadSkillCategoriesFromAPI(): Promise<SkillCategory[]> {
+  return loadSkillCategories();
+}
+
 export async function loadTeams(): Promise<Team[]> {
   try {
     const response = await fetch("/api/teams");