Introduces `PageHeader` component with a back-to-dashboard button and integrates it into AIPage, AnalyticsPage, FinancesPage, TasksPage, and VoicePage. Replit-Commit-Author: Agent Replit-Commit-Session-Id: d7e7c4e8-20cb-41c4-9d0e-79f48938fede
Introduces `PageHeader` component with a back-to-dashboard button and integrates it into AIPage, AnalyticsPage, FinancesPage, TasksPage, and VoicePage. Replit-Commit-Author: Agent Replit-Commit-Session-Id: d7e7c4e8-20cb-41c4-9d0e-79f48938fede