feat: enhanced UI and added pause feature

[Desouki27]

• Main status now prioritizes any Online device, then Standby, then Offline, and the chart state uses the same priority in ContactCard.tsx and Dashboard.tsx.
• Added a state timeline with back/forward time navigation, range presets, and a clearer banded visualization plus breakdown stats in ContactCard.tsx.
• Added history window controls so both RTT and state charts render a stable, sorted slice instead of the full stream in ContactCard.tsx.
• Refreshed the overall UI (fonts, background, glass panels, colors, spacing, buttons, cards, login screens, header chips) in index.css, App.tsx, Dashboard.tsx, ContactCard.tsx, and Login.tsx.
• Implemented pause/resume tracking with Start/Stop toggle plus Delete, and server-side pause state so requests stop without removing the profile in tracker.ts, signal-tracker.ts, server.ts, Dashboard.tsx, and ContactCard.tsx.