feat: add certificate generation system with PDF template and Thai font support

Backend/src/types/certificate.types.ts

@@ -0,0 +1,53 @@
+// ============================================
+// Certificate Types
+// ============================================
+
+export interface GenerateCertificateInput {
+    token: string;
+    course_id: number;
+}
+
+export interface GenerateCertificateResponse {
+    code: number;
+    message: string;
+    data?: {
+        certificate_id: number;
+        file_path: string;
+        download_url: string;
+        issued_at: Date;
+    };
+}
+
+export interface GetCertificateInput {
+    token: string;
+    course_id: number;
+}
+
+export interface GetCertificateResponse {
+    code: number;
+    message: string;
+    data?: {
+        certificate_id: number;
+        course_id: number;
+        course_title: { th: string; en: string };
+        file_path: string;
+        download_url: string;
+        issued_at: Date;
+    };
+}
+
+export interface ListMyCertificatesInput {
+    token: string;
+}
+
+export interface ListMyCertificatesResponse {
+    code: number;
+    message: string;
+    data: {
+        certificate_id: number;
+        course_id: number;
+        course_title: { th: string; en: string };
+        download_url: string;
+        issued_at: Date;
+    }[];
+}