Migrate subscription cleanup to takeUntilDestroyed

Description

Components across the codebase manage observable subscriptions manually with Subscription[] arrays and ngOnDestroy cleanup. Angular 16+ provides takeUntilDestroyed() from @angular/core/rxjs-interop which automatically unsubscribes when a component is destroyed — no OnDestroy boilerplate needed. This ticket migrates all components to that pattern, which also fixes ~18 components that currently have no cleanup at all.

Acceptance Criteria

• All components using manual Subscription[] + ngOnDestroy cleanup are migrated to takeUntilDestroyed()
• All components that currently lack cleanup (~18) are fixed by adding takeUntilDestroyed() to their subscribe pipes
• Remove OnDestroy implementations that only exist for subscription cleanup
• No behavioral changes — only lifecycle cleanup approach changes
• Run ng build to verify no regressions

Proposed Solution

Import DestroyRef and takeUntilDestroyed from @angular/core/rxjs-interop. Inject DestroyRef, then pipe each observable through takeUntilDestroyed() before subscribing. Remove the Subscription[] array, the push calls, and the ngOnDestroy forEach unsubscribe block. Start with the ~18 components missing cleanup entirely, then migrate the ~25 components that already have manual cleanup. Test with ng build.