Draft: feat/ui-vitals-history-enhancement

Summary

Enhanced the Vitals History section for improved readability and consistency.

Changes

Standardized vital display format (e.g., BP: 120/80, HR: 78)

Replaced missing values (____) with -

Unified BP display with fallback logic

Added relevant icons for each vital

Preserved high/low/normal color indicators (applied only to values)

Scope

UI-only changes. No backend or API modifications.