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/skill-file-loader.ts

@@ -0,0 +1,94 @@
+import fs from "fs";
+import path from "path";
+import { SkillCategory } from "./types";
+
+/**
+ * Load all skill categories from JSON files in the data/skills directory
+ */
+export function loadSkillCategoriesFromFiles(): SkillCategory[] {
+  const dataDir = path.join(process.cwd(), "data", "skills");
+  const skillCategories: SkillCategory[] = [];
+
+  try {
+    // Read all JSON files in the skills directory
+    const files = fs
+      .readdirSync(dataDir)
+      .filter((file) => file.endsWith(".json"));
+    console.log(`📁 Found ${files.length} JSON files: ${files.join(", ")}`);
+
+    // Load all JSON files
+    for (const file of files) {
+      const filePath = path.join(dataDir, file);
+      const categoryName = path.basename(file, ".json");
+
+      try {
+        console.log(`📖 Loading ${file}...`);
+        const fileContent = fs.readFileSync(filePath, "utf-8");
+        const data = JSON.parse(fileContent);
+
+        // Validate that it's a proper SkillCategory
+        if (data.category && data.icon && Array.isArray(data.skills)) {
+          skillCategories.push(data);
+        } else {
+          console.warn(`⚠️ Invalid skill category format in ${file}`);
+        }
+      } catch (error) {
+        console.error(`❌ Error loading ${file}:`, error);
+        // Continue with other files instead of failing completely
+      }
+    }
+
+    console.log(`📊 Successfully loaded ${skillCategories.length} categories`);
+    return skillCategories;
+  } catch (error) {
+    console.error("❌ Error reading skills directory:", error);
+    return [];
+  }
+}
+
+/**
+ * Get the list of available skill category files
+ */
+export function getSkillCategoryFiles(): string[] {
+  try {
+    const dataDir = path.join(process.cwd(), "data", "skills");
+    return fs
+      .readdirSync(dataDir)
+      .filter((file) => file.endsWith(".json"))
+      .map((file) => path.basename(file, ".json"));
+  } catch (error) {
+    console.error("❌ Error reading skills directory:", error);
+    return [];
+  }
+}
+
+/**
+ * Load a specific skill category by filename
+ */
+export function loadSkillCategoryFromFile(
+  categoryName: string
+): SkillCategory | null {
+  try {
+    const dataDir = path.join(process.cwd(), "data", "skills");
+    const filePath = path.join(dataDir, `${categoryName}.json`);
+
+    if (!fs.existsSync(filePath)) {
+      console.warn(`⚠️ Skill category file not found: ${categoryName}.json`);
+      return null;
+    }
+
+    const fileContent = fs.readFileSync(filePath, "utf-8");
+    const data = JSON.parse(fileContent);
+
+    // Validate that it's a proper SkillCategory
+    if (data.category && data.icon && Array.isArray(data.skills)) {
+      return data;
+    } else {
+      console.warn(`⚠️ Invalid skill category format in ${categoryName}.json`);
+      return null;
+    }
+  } catch (error) {
+    console.error(`❌ Error loading skill category ${categoryName}:`, error);
+    return null;
+  }
+}