refactor(ui): standardize page layouts and component styling

Introduce structural CSS classes for page shells, headers, and surface cards
Update primary theme color to red and neutral to zinc across the application

AGENTS.md

@@ -29,6 +29,17 @@ The Git history follows Conventional Commit-style messages, commonly `feat(scope
 
 Create local configuration from `.env.example`. Do not commit secrets, session keys, database URLs with credentials, or WhatsApp tokens. Keep `NUXT_PUBLIC_APP_URL` aligned with the browser origin because WebAuthn requires a stable relying-party origin.
 
+## UI Safety Rules (CRITICAL)
+
+User-facing UI must NEVER contain:
+
+- prompts
+- remarks
+- planning notes
+- debug messages
+- explanations of what was changed
+- internal field names like `debug`, `meta`, `internal`
+
 ## Agent-Specific Instructions
 
 Keep implementations concise and scoped to the requested behavior. Prefer the smallest code change that fits existing patterns, and avoid unrelated refactors, formatting churn, or broad rewrites.