deps: update next.js to 15.5.9 #385

Job	Run time
Security & Code Quality	1m 56s
Test Suite	46s
Build & Performance	4m 40s
Database Tests	1m 1s
Enhanced Security Testing	5m 19s
Performance Monitoring	0s
Deploy to Production	-1s
Deploy to Staging	-1s
Performance Monitoring (Staging)	0s
Rollback on Failure	0s
	13m 40s

Provide feedback