style: change role terminology from Full-Stack to Backend Developer

src/components/About/About.tsx

@@ -50,10 +50,10 @@ export default function About() {
         {/* Left Column: Biography & Stats */}
         <div className="flex flex-col gap-6">
           <p className="text-base leading-relaxed text-text-secondary">
-            I am a final-year Information Technology student at Posts and Telecommunications Institute of Technology (PTIT HCMC), majoring in Software Engineering. My passion lies in Full-Stack Web Development, where I enjoy bridging the gap between secure, scalable backend services and responsive, polished frontend layouts.
+            I am a final-year Information Technology student at Posts and Telecommunications Institute of Technology (PTIT HCMC), majoring in Software Engineering. My passion lies in Backend Development, where I enjoy building secure, scalable backend services and designing robust APIs.
           </p>
           <p className="text-base leading-relaxed text-text-secondary">
-            Through my academic curriculum and dedicated personal projects, I have gained hands-on experience building RESTful APIs using Java and Spring Boot, securing endpoints with Spring Security and JWT, and constructing interactive user interfaces with React and Next.js. I am looking for a Full-Stack Developer Internship to apply my skills, learn from experienced mentors, and contribute to real-world software products.
+            Through my academic curriculum and dedicated personal projects, I have gained hands-on experience building RESTful APIs using Java and Spring Boot, securing endpoints with Spring Security and JWT, and constructing interactive user interfaces with React and Next.js. I am looking for a Backend Developer Internship to apply my skills, learn from experienced mentors, and contribute to real-world software products.
           </p>
 
           {/* Academic Stats Cards */}

src/components/Hero/Hero.tsx

@@ -38,7 +38,7 @@ export default function Hero() {
         </div>
         <h1 className="text-5xl sm:text-7xl font-extrabold mb-6 leading-[1.05] tracking-tighter text-text-primary">
           Hi, I am <span className="bg-gradient-to-r from-text-primary to-text-secondary bg-clip-text text-transparent">Bui Minh Quan</span>
-          <span className="bg-gradient-to-r from-primary to-secondary bg-clip-text text-transparent block">Full-Stack Developer</span>
+          <span className="bg-gradient-to-r from-primary to-secondary bg-clip-text text-transparent block">Backend Developer</span>
         </h1>
         <p className="text-base sm:text-lg text-text-secondary mb-8 leading-relaxed max-w-[500px]">
           Information Technology student at PTIT HCMC specializing in Software Engineering.