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.

app/api/skills/migrate/route.ts

@@ -0,0 +1,52 @@
+import { NextResponse } from "next/server";
+import { SkillsService } from "@/services";
+import { loadSkillCategoriesFromFiles } from "@/lib/skill-file-loader";
+
+export async function POST() {
+  try {
+    console.log("🚀 Starting skills migration via API...");
+
+    // Load all skill categories from JSON files
+    const skillCategories = loadSkillCategoriesFromFiles();
+
+    console.log(`📊 Found ${skillCategories.length} categories`);
+
+    const totalSkills = skillCategories.reduce(
+      (sum, cat) => sum + cat.skills.length,
+      0
+    );
+    console.log(`🎯 Total skills to migrate: ${totalSkills}`);
+
+    // Bulk insert into database
+    await SkillsService.bulkInsertSkillsFromJSON(skillCategories);
+
+    console.log("✅ Skills migration completed successfully!");
+
+    // Verify the migration
+    const categoriesFromDb = await SkillsService.getSkillCategories();
+    const totalSkillsInDb = categoriesFromDb.reduce(
+      (sum, cat) => sum + cat.skills.length,
+      0
+    );
+
+    return NextResponse.json({
+      success: true,
+      message: "Skills migration completed successfully",
+      stats: {
+        categoriesMigrated: skillCategories.length,
+        skillsMigrated: totalSkills,
+        categoriesInDb: categoriesFromDb.length,
+        skillsInDb: totalSkillsInDb,
+      },
+    });
+  } catch (error) {
+    console.error("❌ Migration failed:", error);
+    return NextResponse.json(
+      {
+        error: "Failed to migrate skills",
+        details: error instanceof Error ? error.message : "Unknown error",
+      },
+      { status: 500 }
+    );
+  }
+}