Align application UI with Foundation design system

[jasonhedman]

Summary

• replace route-level visual overrides with semantic design-system typography, buttons, alerts, badges, fields, cards, and dialog composition
• reorganize the authenticated workspace page and its private components and tests under the workspace route group without changing the public URL
• align the authenticated sidebar header, navigation, and footer with the shadcn Base UI composition and keep sidebar sizing in the UI primitive
• remove redundant global CSS that overrode component typography, and normalize deployment setup states for Google Workspace and Vercel Blob
• simplify chat, task, vault, and sign-in surfaces while preserving their existing behavior

Validation

• pnpm check
• production build with documented local placeholder environment values
• 225 tests passed
• desktop and mobile visual verification of the authenticated sidebar and key application routes