feat: TUI for download progress and stream management

[biodrone]

Overview

Add a terminal UI (TUI) for StreamDL that shows real-time download progress, active streams, and VOD queue status.

Context

Currently all output is via log lines — no structured progress visibility. The VOD feature (#551) is adding FFmpeg progress parsing that will provide the data source (speed, percentage, ETA) for a TUI to consume.

Scope options (TBD)

• Minimal: Live table of active downloads with progress bars (bubbletea/lipgloss)
• Medium: Multi-pane with downloads, VOD queue, and log panels
• Full: Interactive — browse channels, trigger downloads, manage queue, view history

Dependencies

• VOD support (feat: Twitch VOD support #551) — adds FFmpeg progress parsing and SQLite download history
• Should be a separate feature branch after VOD lands

Tech candidates

• bubbletea — Go TUI framework
• lipgloss — styling
• bubbles — progress bars, tables, etc.