feat: concurrent wallet scanning with real-time progress bar (Fixes #29)

[lb1192176991-lab]

What

Speeds up solana-rug wallet <ADDR> by scanning tokens concurrently and adds a real-time progress bar.

Implementation

New function: rug_check_wallet_concurrent(address)

• Uses concurrent.futures.ThreadPoolExecutor (stdlib — zero new deps)
• Default 4 workers, configurable via WALLET_SCAN_WORKERS env var (max 10)
• Falls back to sequential mode when workers=1 or <=2 tokens
• Thread-safe wrapper _rug_check_token_safe() catches all exceptions

Progress bar

• Format: [████████░░] 45/500 (9%) | 3 risks | 12s elapsed ETA:2m30s
• Uses carriage return (\r) — no scroll spam
• Auto-disables when stdout is not a TTY (piped/JSON mode)
• Tracks: completed count, risks found, elapsed time, estimated remaining
• Unicode blocks: █ for completed, ░ for remaining

Compatibility

• --sequential flag restores original sequential behavior
• WALLET_SCAN_WORKERS=1 also forces sequential mode
• Original rug_check_wallet() preserved unchanged
• Results sorted by safety score ascending (riskiest first)

Env vars

Variable	Default	Description
WALLET_SCAN_WORKERS	4	Concurrent workers (1-10)

Fixes: #29

[codegraphtheory]

Superseded by #43 which was merged. KHHH2312 submitted a PR for the same issue first. Bounty for #29 awarded to them. Thanks for contributing!