refactor: remove obsolete scaffolding and dead modules

Drop the unused root hello-world controller, empty CommonModule imports, development seeding code, legacy student report entity, stale DTOs, notification hook, and their placeholder tests.

apps/server/src/deposits/dto/deposit.dto.ts

@@ -24,15 +24,6 @@ export class CreateInstallmentDto {
   dueDate: string;
 }
 
-export class UpdateInstallmentDto {
-  @IsOptional()
-  @IsString()
-  paidDate?: string;
-
-  @IsOptional()
-  @IsString()
-  status?: string;
-}
 
 
 export class RefundDepositDto {
@@ -57,9 +48,3 @@ export class CreateDepositWithInstallmentsDto extends CreateDepositDto {
   @Type(() => CreateInstallmentDto)
   installments?: CreateInstallmentDto[];
 }
-
-export class ApproveRefundDto {
-  @IsOptional()
-  @IsString()
-  notes?: string;
-}