We currently have inconsistent button alignments: some buttons are left-aligned (Subscribe, admin forms) and others are centered (Unsubscribe card).

Define a clear rule — button alignment should follow the content alignment of its container (left-aligned content → left button, centered content → centered button) — and apply it consistently across all pages: Subscribe, Unsubscribe, 404, admin login, admin dashboard.

Buttons should always use the compact btn-primary class, never full-width unless decided otherwise