fix: add explicit timestamp type for Message.pinned_at column

TypeORM cannot infer the correct PostgreSQL column type for Date | null
without an explicit type annotation. This caused a runtime
DataTypeNotSupportedError when connecting to postgres.

Co-Authored-By: Erkin Alp Güney <erkinalp9035@gmail.com>

Author: devin-ai-integration[bot]

src/util/entities/Message.ts

@@ -190,7 +190,7 @@ export class Message extends BaseClass {
     @Column({ nullable: true })
     pinned?: boolean;
 
-    @Column({ nullable: true })
+    @Column({ type: "timestamp", nullable: true })
     pinned_at?: Date | null;
 
     @Column({ type: "int" })