feat: Context-aware journal prompts, sleep correlation tracker, and dark/light mode toggle

feat: Live Vocal Stress Meter — real-time SVG gauge with needle, pitch/energy sub-metrics, and spectral analysis during recording

InnerVoice Production Upgrade: Multi-channel chat, premium UI components, Whisper-small accuracy upgrade, and full-screen layout polishing

feat: implement JWT auth and voice calibration onboarding

Initial commit: InnerVoice MVP